historical trends and concentrations of fecal coliform bacteria in the

U.S. Department of the InteriorU.S. Geological Survey

Historical Trends and Concentrationsof Fecal Coliform Bacteriain the Brandywine Creek Basin,Chester County, Pennsylvaniaby Debra A. Town

Water-Resources Investigations Report 01-4026

Prepared in cooperation with the

CHESTER COUNTY WATER RESOURCES AUTHORITYCHESTER COUNTY HEALTH DEPARTMENT

New Cumberland, Pennsylvania2001

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U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information Copies of this report may bewrite to: purchased from:

District Chief U.S. Geological SurveyU.S. Geological Survey Branch of Information Services215 Limekiln Road Box 25286New Cumberland, Pennsylvania 17070-2424 Denver, Colorado 80225-0286

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CONTENTS

Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Description of study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Fecal-indicator bacteria and water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Methods of site selection, data collection, and data analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Data collection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Spatial analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Historical trends in fecal coliform bacteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Factors affecting bacteria concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Land use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Field-measured properties of water and streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Seasonality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Effect of reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Comparison of bacteria concentrations during base flow and stormflow. . . . . . . . . . . . . . . . . . . . . . . . . . . 17Extent and potential sources of fecal and Escherichia Coli bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

West Branch Brandywine Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19East Branch Brandywine Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Main Stem Brandywine Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Point discharges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Selected references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

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ILLUSTRATIONS

Page

Figures 1-2. Maps showing:1. Location of Brandywine Creek Basin, Chester County, Pennsylvania. . . . . . . . . .22. Sampling sites in the Brandywine Creek Basin, 1998-99 . . . . . . . . . . . . . . . . . . . . .6

figures 3-4. Graphs showing:3. Annual median concentrations of fecal coliform bacteria at Brandywine

Creek at Chadds Ford, East Branch Brandywine Creek belowDowningtown, and West Branch Brandywine Creek at Modena,1973-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

4. Relation between streamflow and concentration of fecal coliform bacteria,Brandywine Creek at Chadds Ford, East Branch Brandywine Creekbelow Downingtown, and West Branch Brandywine Creek atModena, 1973-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

figures 5-10. Boxplots showing:5. Distribution of annual median concentrations of fecal coliform bacteria at

three USGS long-term water-quality monitor and streamflow-measurement stations during base flow and stormflow, BrandywineCreek Basin, 1973-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

6. Distribution of concentrations of fecal coliform bacteria during base flowand stormflow at sites in agricultural, forested, residential, and mixedsubbasins, Brandywine Creek Basin, 1998-99. . . . . . . . . . . . . . . . . . . . . . . . . .12

7. Distribution of monthly water temperatures during base flow andstormflow at West Branch Brandywine Creek at Modena, East BranchBrandywine Creek below Downingtown and Brandywine Creek atChadds Ford, 1990-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

8. Distribution of monthly fecal coliform bacteria concentrations for baseflow and stormflow, West Branch Brandywine Creek at Modena,East Branch Brandywine Creek below Downingtown, andBrandywine Creek at Chadds Ford, 1990-99 . . . . . . . . . . . . . . . . . . . . . . . . . .15

9. Distribution of concentrations of fecal coliform bacteria during base flowand stormflow at sampling sites above and below Chambers LakeReservoir, Rock Run Reservoir, and Marsh Creek Reservoir, 1998-99 . . . . .16

10. Distribution of fecal coliform bacteria concentrations during base flow andstormflow at selected sampling sites in the Brandywine Creek Basin,1998-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

figures 11-12. Maps showing median concentrations of fecal coliform bacteria:11. During base flow, Brandywine Creek Basin, 1998-99 . . . . . . . . . . . . . . . . . . . . . . .2012. During stormflow, Brandywine Creek Basin, 1998-99 . . . . . . . . . . . . . . . . . . . . . .21

figures 13-15. Boxplots showing distribution of concentrations of fecal coliform bacteria:13. During base flow and stormflow at sampling sites on West Branch

Brandywine Creek, 1998-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2214. During base flow and stormflow at sampling sites on East Branch

Brandywine Creek, 1998-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2715. During base flow and stormflow at sampling sites on main stem

Brandywine Creek, 1998-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

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TABLES

Page

Table 1. Sites sampled for bacteria, Brandywine Creek Basin, Chester County, Pennsylvania . . . . . .42. Indicator bacteria, filter size, ideal count range, holding times, and incubation time

and temperature for collected bacteria samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73. Quality-control results for fecal coliform and E. coli bacteria, Brandywine Creek Basin,

1998-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84. Spearman rank correlations significant at the 95-percent confidence interval for base-

flow and stormflow samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135. Range and median concentrations of fecal coliform bacteria during base flow and

stormflow for five sites in the Brandywine Creek Basin, 1998-99 . . . . . . . . . . . . . . . . . . . .17table 6-11. Streamflow, physical and chemical properties, and fecal coliform and

E. coli bacteria concentrations:

6. During base flow, West Branch Brandywine Creek Basin, July 1998to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

7. During base flow, East Branch Brandywine Creek Basin, July 1998to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

8. During base flow, main stem Brandywine Creek Basin, July 1998to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

9. During storms, West Branch Brandywine Creek Basin, July 1998to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

10. During storms, East Branch Brandywine Creek Basin, July 1998to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

11. During storms, main stem Brandywine Creek Basin, July 1998to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

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CONVERSION FACTORS AND ABBREVIATIONS

Temperature: Temperature is given in degrees Celsius (°C), which can be converted to degrees Fahrenheit(°F) by use of the following equation:

°F = 1.8 (°C) + 32

Concentrations of bacteria are given in colonies per 100 milliliters (col/100 mL), which is the same ascolony forming units per 100 milliliters (CFU/100 mL).

Other abbreviations used in report:

mg/L milligrams per litermS/cm microsiemens per centimeter at 25 degrees CelsiusmL millilitersE. coli Escherichia coli, a fecal-indicator bacteriummTEC Membrane filter media for Escherichia coliCWA Clean Water ActDMR Discharge Monitoring ReportUSGS U.S. Geological SurveyUSEPA U.S. Environmental Protection AgencyPaDEP Pennsylvania Department of Environmental ProtectionCCWRA Chester County Water Resources AuthorityCCHD Chester County Health Department

Multiply By To obtaininch (in.) 2.54 centimeterfoot (ft) 0.3048 metermile (mi) 1.609 kilometersquare mile (mi2) 2.590 square kilometercubic foot per second (ft3/s) 0.02832 cubic meter per second

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ABSTRACT

The Brandywine Creek in Chester County is usedfor recreation and as an important source of drinkingwater. For this study, 40 sites were established forcollection of water samples for analysis of fecal coliformand Escherichia coli bacteria in 1998-99. Samples werecollected during base-flow conditions and during fivestorms in which rainfall exceeded 0.5 inch. During base-flow conditions, the median concentrations of fecalcoliform bacteria exceeded 200 col/100 mL at 26 of the40 sites (65 percent). During stormflow conditions, themedian concentration of fecal coliform bacteria exceededthe Pennsylvania Department of EnvironmentalProtection (PaDEP) criterion of 200 col/100 mL at 30 of33 sites sampled (91 percent). Trends in fecal coliformbacteria concentrations were downward for the period1973-99 at three long-term water-quality monitorstations, the result of upgrades in wastewater treatmentplants, decreases in point-source discharges, and adecrease in agricultural land. A positive relation existsbetween streamflow and concentrations of fecal coliformbacteria at two of the long-term stations, butconcentrations are elevated in base flow and stormflowat all three stations.

Factors affecting bacteria concentrations in theBrandywine Creek Basin include nonpoint-sourcecontaminants, reservoirs, seasonality, and stormflow.Nonpoint sources of bacterial contamination in thebasin include, but are not limited to, land-surfacerunoff, urbanization, agricultural processes, ground-water contamination, and wildlife. Bacteria concen-trations in streams that flow directly from the reservoirsare much lower than the concentrations in the streamsflowing into the reservoirs. During March, April, May,October, and November, the Brandywine Creek tends tohave lower water temperatures and bacteriaconcentrations than during June, July, August, andSeptember. The 10-year median concentrations of

bacteria at West Branch Brandywine Creek at Modenaand East Branch Brandywine Creek belowDowningtown exceed the criterion of 200 col/100 mLestablished by the PaDEP during the swimming season.The 10-year median concentrations of bacteria atBrandywine Creek at Chadds Ford exceed the criterionof 200 col/100 mL only during June. None of thestations exceed the criterion of 2,000 col/100 mL asestablished by the PaDEP for the remainder of the year.

INTRODUCTION

The aesthetic, recreational, and ecologicalhealth of the Brandywine Creek in Chester Countymay be influenced by high concentrations of fecalcoliform bacteria. Chapter 93 of the “PennsylvaniaWater Quality Standards” lists the following asuses for the Brandywine Creek: water supply(potable, industrial, and livestock), irrigation,aesthetics, boating and fishing, wildlife watersupply, trout stocking, and fishes (warmwater,coldwater, and migratory) (PennsylvaniaDepartment of Environmental Protection, 1999,p. 62). Five public water suppliers in ChesterCounty withdraw water from the BrandywineCreek for domestic, commercial, and industrialuse. Three reservoirs on the creek play host toboaters, fishermen, and canoeists (Grieg andothers, 1998).

As part of a cooperative program among theChester County Water Resources Authority(CCWRA), Chester County Health Department(CCHD), and the U.S. Geological Survey (USGS),fecal coliform bacteria, temperature, pH, dissolvedoxygen, and specific conductance of theBrandywine Creek are measured at the WestBranch Brandywine Creek at Modena (USGSstation number 01480617), the East BranchBrandywine Creek below Downingtown (USGS

HISTORICAL TRENDS AND CONCENTRATIONSOF FECAL COLIFORM BACTERIAIN THE BRANDYWINE CREEK BASIN,CHESTER COUNTY, PENNSYLVANIA

by Debra A. Town

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station number 01480870), and the main stem ofthe Brandywine Creek at Chadds Ford (USGSstation number 01481000) (fig. 1). Temperature,pH, dissolved oxygen, and specific conductanceare measured hourly, and concentrations of fecalcoliform bacteria are measured bi-weekly. Datahave been collected from March to November(Wood, 1998) since 1973 at main stem BrandywineCreek at Chadds Ford, since 1980 at East BranchBrandywine Creek below Downingtown, and since1981 at West Branch Brandywine Creek at Modena.

Data from the long-term water-quality monitorstations show that concentrations of fecal coliformbacteria during storms typically are greater thanthose during base flow. Water samples containingfecal coliform bacteria typically contain Escherichia

coli (E. coli) bacteria, which indicate the potentialpresence of water-borne pathogens that maypresent a public health risk for humans thatconsume or have bodily contact with contaminatedwater (Dufour, 1977).

This study supports the objectives and goals ofChester County’s Landscapes program (ChesterCounty, 1996, p. 114). The study will help toachieve and sustain a high-quality natural resourcesystem and will help to protect public health andsafety. This report also reinforces the Phase I and IIresults of the Christina River Basin Water QualityManagement Strategy (Grieg and others, 1998).The Christina project aims at improving waterquality and addressing nonpoint-source pollutionreduction; the CCWRA is a local coordinator.

Figure 1. Location of Brandywine Creek Basin, Chester County, Pennsylvania.

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Purpose and Scope

This report identifies trends in historicalconcentrations of fecal coliform bacteria at threeUSGS long-term water-quality monitor andstreamflow-measurement stations on theBrandywine Creek from 1973 to 1999. Relationsbetween concentrations of fecal coliform bacteriaand streamflow also are compared for the stations.This report discusses the extent and possible typesof sources for fecal coliform and E. coli bacteria inthe Brandywine Creek Basin. Bacteria data, fieldchemistry, and streamflow measurements werecollected by the USGS at 40 sites on the Brandy-wine Creek during July through October 1998 andMarch through September 1999 during base flowand stormflow. Relations between fecal coliformbacteria and field chemistry constituents aredetermined. Relations between land use andconcentrations of fecal coliform bacteria arecompared. The effect of the three reservoirs in thebasin on bacteria concentrations is evaluated.Other factors, such as the ratio of E. coli to fecalcoliform bacteria in water samples and seasonality,are discussed. Water-sample analyses areevaluated to determine the current extent ofbacterial contamination from the subbasins in theBrandywine Creek Basin.

The length of the study and the number of sitesdetermined that the evaluation of potential sourcesfor bacteria would be limited to the subbasin levelwithin the basin rather than specific sources forbacteria. Bacterial contamination is identified onthe basis of the median concentration of fecalcoliform bacteria for each subbasin during baseflow and stormflow.

Ackno wledgments

The author gratefully acknowledges theassistance of Linda Tracey of the CCHD, who wasa tremendous asset with the interlaboratoryquality assessment of the bacteria analyses. Inaddition, USGS interns Carrie Gillespie, TammiRenninger, and Kiley McDaniel contributed a greatdeal of time and effort to the data-collection phaseof the project along with USGS staff membersKevin Grazul, Cynthia Rowland-Lesitsky, andAbdul Mohammad. The cartography in this reportwas completed by Scott Hoffman of the USGS inLemoyne, Pa.

Description of the Stud y Area

The Brandywine Creek Basin drainage area isapproximately 325 mi2, most of which is in ChesterCounty, Pa. The estimated population in 1998 was197,460 (Greig and others, 1998). The BrandywineCreek is one of four streams that constitute thelarger Christina River Basin, which drains to theDelaware River. Land use in the West BranchBrandywine Creek Basin is predominantlyagricultural with an urban area around the city ofCoatesville. The East Branch Brandywine CreekBasin is predominantly forested with an urbanarea around the borough of Downingtown. Themain stem basin is predominantly agricultural.The Brandywine Creek is lined by forest for mostof its length.

The Brandywine Creek Basin lies in thePiedmont Physiographic Province. Typically,diabase, gneiss, and marble are found north of theGreat Valley. The borough of Downingtown andthe City of Coatesville lie in the Great Valley, whichis underlain by limestone and dolomite and cuts amidline through the basin. Schists and gneissesmake up the bedrock of the southern part of thebasin.

The Brandywine Creek attracts canoeists,fisherman, waders, and even cyclists and hikerswho use the paved areas beside the creek to bikeand walk. While most of these activities arepursued during the swimming season, recreationaluse around the creek goes on year-round.

Latitude and longitude locations wereestablished for each of the 40 sampling sites alongthe Brandywine Creek (table 1). A USGS station-identification number, station name, local alpha-numeric identification number, drainage area ofeach site’s subbasin, and the subbasin’s land-usepercentages also are listed.

FECAL-INDICATOR BACTERIAAND WATER QUALITY

Fecal coliform bacteria are present in waterwhen bacterial pathogens from fecalcontamination are present. Indicator organisms,such as fecal coliform bacteria, are not usuallypathogenic but rather indicate the possiblepresence of pathogenic organisms. Because fecalcoliform bacteria are present in higherconcentrations than the actual pathogens andbecause they can survive longer, the bacteria aremore likely to be detected. Fecal coliform bacteria

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Table 1. Sites sampled for bacteria, Brandywine Creek Basin, Chester County, Pennsylvania

[ID, identification number; USGS, U.S. Geological Survey; WB, West Branch; EB, East Branch; MS, main stem]

LocalID

USGSsite ID

Site name Latitude Longitude

Drainagearea

(squaremiles)

Percentage land use

Agricultural Forested Residential Urban

WB1 01480269 WB Brandywine Creek at Rockville 40 04 50 75 52 20 5.68 72.0 11.0 9.0 0.5WBA 01480295 Two Log Run at Birdell 40 04 06 75 52 25 2.75 34.0 54.0 9.9 1.0WB2 101480300 WB Brandywine Creek near Honey Brook 40 04 22 75 51 40 18.4 68.0 20.0 7.0 1.0WB3 01480349 WB Brandywine Creek at Brandamore 40 02 39 75 49 51 24.0 58.0 27.0 10.0 1.0WB4 01480390 Birch Run near Martins Corner 40 01 50 75 52 20 2.48 30.0 54.0 13.0 8.0WB5 101480400 Birch Run near Wagontown 40 01 38 75 50 43 4.66 31.0 53.0 13.0 2.0WB6 01480458 Rock Run near Philipsville 40 00 20 75 52 44 2.32 58.0 29.0 10.0 2.0WBE 01480463 Rock Run at Reservoir near Coatesville 40 00 07 75 51 20 5.11 52.0 26.0 17.0 2.0WB7 01480466 Rock Run below Coatesville Reservoir 40 00 22 75 51 09 5.56 49.0 26.0 16.0 2.0WBD 01480470 Rock Run at Rock Run near Coatesville 39 59 34 75 49 53 45.5 47.0 33.0 14.0 2.0WBB 01480434 WB Brandywine Creek at Rock Run 39 59 36 75 49 41 37.6 48.0 33.0 14.0 1.0WBC 01480480 WB Brandywine Creek below Rock Run at

Coatesville39 59 28 75 49 52 45.7 47.0 33.0 15.0 2.0

WB8 101480500 WB Brandywine Creek at CoatesvilleReservoir

39 59 08 75 49 40 46.0 47.0 33.0 15.0 2.0

WB9 101480617 WB Brandywine Creek at Modena 39 57 42 75 48 06 55.3 42.0 33.0 16.0 4.0WB10 01480629 Buck Run at Doe Run 39 55 46 75 49 24 21.5 58.0 26.0 11.0 2.0WB11 014806318 Doe Run above tributary at Springdell 39 54 25 75 49 42 8.76 76.0 15.0 5.1 1.0WB12 01480634 WB Brandywine Creek near Embreeville 39 56 04 75 45 00 116.0 53.0 30.0 12.0 3.0WB13 01480637 Little Broad Run near Marshallton 39 57 38 75 42 44 1.02 38.0 27.0 26.0 5.0WB14 01480638 Broad Run at Northbrook 39 55 49 75 41 06 6.38 37.0 29.0 29.0 3.0WB15 01480640 WB Brandywine Creek at Wawaset 39 55 34 75 39 47 134.0 52.0 30.0 12.0 3.0EB1 01480648 EB Brandywine Creek near Cupola 40 05 41 75 51 14 6.86 60.0 25.0 7.0 1.0EB2 01480653 EB Brandywine Creek at Glenmoore 40 05 48 75 46 44 16.2 53.0 34.0 7.0 .4EB3 01480658 Indian Run at Springton 40 04 32 75 46 55 4.26 37.0 46.0 12.0 3.0EB4 101480675 Marsh Creek near Glenmoore 40 05 52 75 44 31 8.53 39.0 46.0 8.0 3.0EB5 101480685 Marsh Creek near Downingtown 40 03 19 75 43 00 20.1 34.0 38.0 17.0 2.0EB6 01480660 EB Brandywine Creek at Lyndell 40 03 34 75 44 39 27.1 45.0 39.0 10.0 1.0EB7 01480662 Culbertson Run at Lyndell 40 03 29 75 45 07 4.41 44.0 33.0 21.0 1.0EB8 101480700 EB Brandywine Creek near Downingtown 40 02 05 75 42 32 60.0 39.0 37.0 16.0 2.0EB9 01480775 Beaver Creek near Downingtown 40 00 12 75 43 28 16.5 33.0 29.0 25.0 4.0EBA 01480800 EB Brandywine Creek at Downingtown 40 00 19 75 42 18 76.4 36.0 36.0 19.0 3.0EBC 01480840 EB Brandywine Creek at Altor 39 58 33 75 40 59 89.0 34.0 37.0 20.0 3.0EB13 01480878 Uwchlan Run at Exton 40 01 35 75 39 52 1.50 67.0 16.0 10.0 2.0EBB 01480887 Valley Creek at Ravine Road near

Downingtown39 59 55 75 39 52 14.4 20.0 31.0 26.0 7.0

EB10 101480870 EB Brandywine Creek belowDowningtown

39 58 07 75 40 25 89.7 34.0 37.0 20.0 3.0

EB11 01480905 Valley Creek at Altor 39 58 12 75 39 59 20.6 30.0 33.0 19.0 7.0EB12 01480930 Taylor Run at Copesville 39 57 19 75 38 55 5.52 23.0 26.0 37.0 4.0EB14 01480950 EB Brandywine Creek at Wawaset 39 55 35 75 38 54 123.0 31.0 35.0 22.0 4.0MS1 01480970 Brandywine Creek at Pocopson 39 54 04 75 37 26 264.0 42.0 32.0 17.0 3.0MS2 01480975 Pocopson Creek at Pocopson 39 54 03 75 38 16 8.57 49.0 21.0 26.0 1.0MS3 101481000 Brandywine Creek at Chadds Ford 39 52 11 75 35 37 288.0 42.0 32.0 18.0 3.0

1 USGS streamflow-measurement station.

5

are easy to culture and typically are harmless tohumans; therefore, they were chosen as theprimary indicator bacteria. Because fecal coliformbacteria were sampled from 1973 to 1999 in theBrandywine Creek, the historical data could becompared with data collected for this study.The Pennsylvania Department of EnvironmentalProtection (PaDEP) and the U.S. EnvironmentalProtection Agency (USEPA) have the same set ofcriteria on the basis of water use. For bathing (full-body contact) in recreational freshwater, on thebasis of a statistically sufficient number of samples(generally not less than five samples equallyspaced over a 30-day period), the geometric meanof the indicated bacterial densities of fecal coliformshould not exceed 200 col/100 mL during theswimming season (May 1 through September 30)and should not exceed 2,000 col/100 mL for theremainder of the year. (Pennsylvania Departmentof Environmental Protection, 1999, p. 16).For water supply, bacteria concentrations shouldnot exceed 5,000 col/100 mL as a monthly averagein more than 20 percent of the samples collectedduring a month and should not exceed20,000 col/100 mL in more than 5 percent of thesamples (Pennsylvania Department ofEnvironmental Protection, 1999).

E. coli bacteria are found within the fecalcoliform group in smaller concentrations than fecalcoliform bacteria. E. coli were chosen as thesecondary indicator of bacterial contaminationbecause they are a specific indicator of fecalpollution. E. coli inhabit the gastrointestinal tract ofwarm-blooded animals and are an indicator of thepresence of intestinal pathogens that cause humandiseases (Francy and others, 1993). The USEPA(1998) has set a criterion on the basis of water use.For bathing (full-body contact) in recreationalfreshwater, on the basis of a statistically sufficientnumber of samples (generally not less than fivesamples equally spaced over a 30-day period), thegeometric mean of the indicated bacterial densitiesof E. coli should not exceed 126 col/100 mL.

Fecal-indicator bacteria assess the sanitaryquality of water and include Enterococci, thecoliform group, and the streptococcal group. Forthis study, the coliform group were used as theindicator organisms of choice. Within the coliformgroup, total coliforms (of which fecal coliform andE. coli are part), fecal coliforms (of which E. coli ispart), and E. coli are the most widely usedindicators. Total coliforms, and to some extent fecalcoliforms, have been used as indicators of the

possible presence of pathogens in surface watersand have been associated with a risk of disease onthe basis of epidemiological evidence ofgastrointestinal disorders from ingestion ofcontaminated surface water. Contact withpathogens in contaminated surface water cancause ear or skin infections or respiratory diseases.The pathogens responsible for these diseases canbe bacteria, viruses, protozoans, fungi, or parasitesthat live in the gastrointestinal tract and are shed inthe feces of warm-blooded animals. Because it isdifficult to analyze for this myriad of pathogens,fecal coliform and E. coli bacteria are used as theprimary indicators of fecal contamination inrecreational waters. E. coli is considered to have ahigh degree of association with outbreaks ofcertain diseases and are recommended as a fecal-indicator for bacterial water-quality standards bythe USEPA (1986).

Bacterial contamination can come from pointand nonpoint sources. Point sources are single,identifiable points of origin, such as municipal orindustrial discharges. Nonpoint sources are fromdiffuse origins. Agricultural nonpoint sourcesinclude animal waste, the application of manureand biosolids to fields, and crop irrigation fromcontaminated storage ponds. Urban/residentialnonpoint sources include active construction areas,failed waste-disposal systems, residential septicsystems, pet waste, litter, and landfill leakage.Wildlife waste also is a nonpoint source. TheBrandywine Creek is affected by nonpoint sourcesof bacterial contamination during base flow andespecially during stormflow.

METHODS OF SITE SELECTION,DATA COLLECTION, AND DATA ANALYSIS

Data were collected by the USGS from July toOctober 1998 as part of a reconnaissance samplingof the Brandywine Creek Basin under base-flowconditions to determine preliminary base-flowconcentrations of fecal coliform bacteria. Thisinformation, along with data from the PaDEP andthe CCHD, were used to determine the location ofbase-flow sampling sites. Site locations also wereselected on the basis of land use, known pointdischarges, and areas where recreational use wasevident. Thirty-two sites initially were selected forsample collection. All nine USGS streamflow-measurement stations in the basin were used assampling sites. Eight additional sampling siteswere added midway through the study to pinpoint

6

potential sources of elevated bacteria measuredduring monthly sampling (fig. 2).

Data Collection

Water samples were collected for analysis forfecal coliform and E. coli bacteria at the sitesestablished as a result of the reconnaissancesampling. Sampling frequency was approximatelymonthly from March to September 1999 to provide

sufficient temporal variation and different flowregimes for the evaluation of bacterialcontamination. Fecal coliform bacteria weremeasured monthly at all 40 sites during base flow,and E. coli bacteria were measured monthly at asubset of those 40 sites during base flow. Duringthe course of the study, each of the initial 32 siteswas sampled for E. coli bacteria at least onceduring base flow.

Figure 2. Sampling sites in the Brandywine Creek Basin, Chester County, Pennsylvania,1998-99. (See table 1 for full names and characteristics of sampling sites.)

7

Storm sampling also was conducted as a partof this study. Data were collected during fivestorms in which rainfall exceeded 0.5 in. Most ofthe USGS streamflow-measurement stations weresampled during every storm. The selection of thesestations as sampling sites eliminated the need forcurrent-meter measurements of streamflow.During storms, only specific conductance,temperature, and gage height were measured atthe time the sample was collected. In addition, foreach storm, five sites not at streamflow-measurement stations were sampled.

All water samples were analyzed for fecalcoliform and E. coli bacteria by use of themembrane filtration method described in Myersand Wilde (1997) (table 2). Water samples werecollected as grab samples, by use of individuallylabeled sterile 250-mL plastic bags. The plastic bagwas submerged in the stream at the center of flowand opened to allow water to enter. It was thensealed and placed in a cooler for transportation tothe laboratory. Samples were incubatedimmediately after filtration. CCHD samples werecollected in 250-mL plastic bottles. The bottleswere submerged in the stream in the same place asthe plastic bags, opened and filled with water, andsealed and placed in a cooler for transportation tothe CCHD laboratory.

Field chemistry measurements and streamflowmeasurements were made for all base-flowsamples collected. Field chemistry includeddissolved oxygen, pH, specific conductance, andwater temperature. Dissolved oxygen wasmeasured by use of the Winkler Method (Clesceriand others, 1998). The pH, specific conductance,and water temperature were measured withmeters.

Quality assurance was conducted by USGSand CCHD personnel by use of guidelines fromClesceri and others (1998). Quality-assurancemethods were used in the field and the laboratoryand for the equipment and media. Quality controlwas conducted according to guidelines fromClesceri and others (1998). Quality control forvariability was conducted by use of interlaboratorycomparisons of sequential replicate samples.Duplicate samples were analyzed by the CCHDlaboratory. Quality-control results are shown intable 3. Quality control for bias was conducted byuse of membrane filter equipment blanks withsterile buffered water filtered and plated beforeevery sample to test for contamination.

Data Anal ysis

Bacteria concentrations in samples collectedfrom July to October 1998 and from March toSeptember 1999 from the Brandywine Creek Basinwere compared to maximum acceptableconcentrations established by the PaDEP (1999).

Median concentrations of fecal coliformbacteria were calculated for all 40 sites. A limitednumber of samples were analyzed for E. colibacteria at each site; therefore, medianconcentrations of E. coli bacteria were notdetermined for either base flow or stormflow.

Graphical analyses (boxplots) were used toevaluate water-quality measurements and bacteriaconcentration during base flow and stormflow. Thewater-quality measurements and bacteria-concentration data collected during base flow andstormflow are listed in tables 6-11 at the end of thisreport. Graphical analyses also were used toevaluate historical data at three USGS long-termwater-quality monitoring and streamflow-measurement stations on Brandywine Creek.

Table 2. Indicator bacteria, filter size, ideal count range, holding times, and incubation time and temperature forcollected bacteria samples (from Myers and Wilde, 1997)

[m-FC, fecal coliform media; M-TEC, Escherichia coli media; °C, degrees Celsius]

Indicator bacteria(and media type)

Filter size(microns)

Ideal countrange

(colonies perfilter)

Holdingtime

Incubation time and temperature

Fecal coliform bacteria(m-FC media)

0.65 20-60 6 hours 22 to 26 hours at 44.5°C

Escherichia coli bacteria(m-TEC media)

.45 20-80 6 hours 2 hours at 35.0°C and then 22 to 24 hours at 44.5°C(filter then transferred to urea substrate broth for15 to 20 minutes before counting).

8

Relations between bacteria, chemicalconstituents, and streamflow for data collected in1998-99 were evaluated statistically by use ofSpearman Rank correlations significant at the95-percent confidence interval. Relations wereevaluated at base-flow and stormflow conditions.Relations between bacteria concentrations andland use were evaluated statistically by use of theKruskal-Wallis test.

Spatial Anal ysis

A geographical information system (GIS)spatial analysis was used to determine the land-use percentages of the subbasins within theBrandywine Creek Basin. Land use was dividedinto four categories: agricultural, forested,residential, and urban. The agricultural categoryconsists of cropland, livestock, and pasture.Forested areas are defined as those with more than50 percent cover of deciduous, coniferous, andmixed woody vegetation. The residential categoryconsists of areas of single- and multi-familyresidences. Urban areas include institutions,transportation/utilities, commercial businesses,and industries. All other categories—exampleswould be mining, water, vacant/barren, publicand private open space—constituted a very low

percentage of land use and were not used in thespatial analysis. The Brandywine Creek Basin wasdivided into 40 subbasins relative to each samplingsite. An individual subbasin usually extendedfrom each sampling site to the sampling siteimmediately upstream from it. Where samplingsites were clustered (as in the supplemental sites),a subbasin included both the initial sites andsupplemental sites. A land-use coverage obtainedfrom the Water Resources Agency for New CastleCounty was used to determine the percentages ofeach type of land use within each subbasin.Subbasins with greater than 50 percent of one typeof land use were designated as predominantly thattype of land use. Subbasins with less than50 percent of one type of land use were assigned a“mixed” designation. Although the urban categorywas used to differentiate land use during the GISspatial analysis and did not appear as a predomi-nant land use, it is an indicator of areas of nonpointsource land-surface runoff.

Twenty-five sites were identified as being insubbasins of mixed land use (table 1), 11 sites wereidentified as being in predominantly agriculturalsubbasins, 3 sites were identified as being inpredominantly forested subbasins, and 1 site wasidentified as being in a predominantly residential

Table 3. Quality-control results for fecal coliform and E. coli bacteria,Brandywine Creek Basin, Chester County, Pennsylvania, 1998-99

[ID, identification number; —, no data collected; FC, fecal coliform; EC, E. coli;E, estimated; >, greater than; col/100 mL, colonies per 100 milliliters; CCHD,Chester County Health Department; USGS, U.S. Geological Survey]

Date Local ID Site ID

FC Concentrations(col/100 mL)

EC Concentrations(col/100 mL)

CCHD USGS CCHD USGS

05/04/99 EB4 01480675 23.E 12.E 15.E 2.E05/04/99 EB8 01480700 170 160 150 17005/04/99 EB13 01480950 180 200 150 15007/19/99 WB2 01480300 25,000 > 6,000 2,700 > 8,00007/19/99 WB13 01480637 1,500 2,000.E 1,100 —07/20/99 EB1 01480648 2,000 > 1,200 890.E —08/03/99 EB1 01480648 220 260 180 24008/16/99 WB1 01480269 4,000 5,100 2,700 5,90008/16/99 WB3 01480349 500 590 460 —08/16/99 WB10 01480629 270 310 170 26008/17/99 EB7 01480662 280 300 210 34008/26/99 WB8 01480500 7,600 9,200 2,600 1,400.E09/13/99 WB14 01480638 460 470 530 32009/14/99 EB6 01480660 200 140.E 140 100.E09/15/99 MS2 01480975 220 140 190 18009/16/99 WB6 01480458 > 6,000 540,000.E >1,600.E 16,000.E

9

subbasin. Although urban land use ranged from1-7 percent, no subbasin was identified as pre-dominantly urban. Each subbasin was examined asan individual entity with regards to impact on theBrandywine Creek’s bacteria concentration.

HISTORICAL TRENDS IN FECALCOLIFORM BACTERIA

Data from East Branch Brandywine Creekbelow Downingtown (EB10), West BranchBrandywine Creek at Modena (WB9), andBrandywine Creek at Chadds Ford (MS3) wereevaluated for historical trends (fig. 3). All threeUSGS long-term water-quality monitoring andstreamflow-measurement stations show decreasedbacteria concentrations since the beginning ofrecord collection. The data were collected at thesesites bi-monthly, usually between March toNovember, regardless of flow conditions. OnlyMS3 shows median concentrations of bacteriabelow 200 col/100 mL for most of the time from1992 to 1999. All three sites show elevated medianconcentrations of bacteria in 1980, 1983, and 1989.The elevated median concentrations are on bothbranches and the main stem of Brandywine Creek.

From 1980 to 1999, the median bacteriaconcentrations at EB10 have decreased by a factorof 1,000, showing the most dramatic and consistentimprovement of the three stations. The medianbacteria concentrations at MS3 have decreased byat least a factor of 10 from a peak in 1980. Sincedata collection began in 1973, the median bacteriaconcentrations at MS3 increased until 1980 andthen progressively decreased to below the PaDEPcriterion of 200 col/100 mL. The median bacteriaconcentrations at WB9 showed a peak in 1981,decreased to the PaDEP criterion in 1987, andincreased until 1999 to one-tenth of its highestrecorded median bacteria concentration.

In 1972, the U.S. Congress enacted landmarklegislation, in the form of a statute, to protect theNation’s waters. The Federal Water PollutionControl Act Amendments of 1972 (referred to asthe Clean Water Act of 1972 or CWA), expandedand built upon existing laws designed to controland prevent water pollution. The CWA may havecontributed to the decrease in bacteria concentra-tions between 1972 and 1987. The Clean Water Actof 1977 and the Water Quality Act of 1987, which

Figure 3. Annual median concentrations of fecal coliform bacteria at Brandywine Creek atChadds Ford, East Branch Brandywine Creek below Downingtown, and West BranchBrandywine Creek at Modena, Pennsylvania, 1973-99.

1970 20001975 1980 1985 1990 1995100

1,000,000

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are successive amendments to the 1972 CWA,have continued to strengthen that law.Concentrations of bacteria decreaseddramatically from 1980 to 1987, rose and fellbetween 1987 and 1996, and then stabilizedfrom 1996 to 1999. Possible factors that wouldlower bacteria concentrations are the additionand upgrade of wastewater treatment plants,an expansion of collection systems, decreasesin point-source discharges, and decreases inagricultural land use in the basin.

Comparisons between streamflow andconcentrations of fecal coliform bacteria duringbase flow and stormflow for sites MS3, EB10,and WB9 are shown in figure 4. There is ageneral relation between streamflow andconcentrations of fecal coliform bacteria at sitesMS3 and WB9. When streamflow is elevated,bacteria concentrations tend to be elevated.A relation between streamflow and concentra-tions of fecal coliform bacteria is not apparentat EB10.

Median concentrations of fecal coliformbacteria were highest at WB9 and lowest atMS3 (fig. 5). EB10 had the greatest range inbacteria concentrations.

FACTORS AFFECTING BACTERIACONCENTRATIONS

Numerous factors affect bacteriaconcentrations in the Brandywine Creek. Landuse, the chemical and physical properties ofstream water, seasonality, and reservoirs areall factors that can affect the concentrationof bacteria. Land-use differences in theBrandywine Creek do not appear to affectbacteria concentrations to a statisticallysignificant extent. A moderate positive relationexists between water temperature and fecalcoliform and E. coli bacteria during base flow.Seasonal changes in water temperature caneither promote or inhibit bacteria growth.Water flowing from reservoirs is low inbacteria concentration.

1 100 10,000 1,000,00010

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20

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1,000

2,000

ST

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AM

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W,

CONCENTRATION OF FECAL COLIFORM BACTERIA,

Figure 4. Relation between streamflow and concentration offecal coliform bacteria, Brandywine Creek at Chadds Ford,East Branch Brandywine Creek below Downingtown, and WestBranch Brandywine Creek at Modena, Pennsylvania, 1973-99.

IN COLONIES PER 100 MILLILITERS

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BRANDYWINE CREEKAT CHADDS FORD

EAST BRANCH BRANDYWINE CREEKBELOW DOWNINGTOWN

WEST BRANCH BRANDYWINE CREEKAT MODENA

(MS3)

(EB10)

(WB9)

11

Land Use

Bacteria concentrations in water samples fromsubbasins with agricultural, forested, residential,and mixed land-use settings were compared. TheKruskal-Wallis test was used to test for statisticallysignificant differences in the ranks of concentra-tions of fecal coliform bacteria between land-usecategories at the 95-percent confidence level for allbase-flow and stormflow samples. The test wasrun twice, once for three categories of land use(agricultural, forested, and residential) and oncefor four categories (agricultural, forested,residential, and mixed). In both cases, the Kruskal-Wallis test showed no statistically significantdifference for concentrations of fecal coliformbacteria among the three predominant land-usegroups (agricultural, forested, and residential) orthe second group that included the mixed categoryfor base flow and stormflow.

While there seems to be no direct relationbetween land use and bacteria concentrationswithin a subbasin, bacteria concentrations in baseflow and stormflow are different. The base-flowbacteria concentrations for all four categories are

lower than stormflow concentrations by a factor ofapproximately 10. During base flow andstormflow, the agricultural, forested, residential,and mixed subbasins have approximately the samemedian bacteria concentration. However, theforested subbasins show a much wider range ofbacteria concentrations (fig. 6).

Field-Measured Pr oper tiesof Water and Streamflo w

Relations among bacteria concentrations, field-measured properties of water, and streamflowwere evaluated statistically by use of Spearman-rank correlations. Statistically significant relations(for p < 0.05) were found to exist. Spearman-rankcorrelations significant at the 95-percentconfidence interval are given in table 4.A moderate positive correlation exists betweentemperature and concentration of fecal coliformbacteria (rs = 0.346) and E. coli bacteria (rs = 0.351).Concentrations of bacteria are lower when watertemperatures are less than approximately 15°C(usually during March and April) than when watertemperatures are greater than approximately 15°C(usually from June to September). A weak negative

Figure 5. Distribution of annual median concentrations of fecal coliform bacteria at three USGS long-termwater-quality monitor and streamflow-measurement stations during base flow and stormflow, Brandywine CreekBasin, Chester County, Pennsylvania, 1973-99.

CHADDS FORD DOWNINGTOWN MODENA50

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25TH PERCENTILE

MEDIAN

75TH PERCENTILE

OR EQUAL TO 1.5 TIMESDATA VALUE LESS THAN

THE INTERQUARTILE RANGE

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PaDEP criterion

12

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Figure 6. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow at sites inagricultural, forested, residential, and mixed subbasins, Brandywine Creek Basin, Chester County, Pennsylvania,1998-99.

IN C

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PaDEP criterion

PaDEP criterion

13

correlation exists between dissolved oxygen andconcentration of fecal coliform bacteria (rs = -0.309)and E. coli bacteria (rs = -0.267). When watertemperatures are higher, dissolved oxygenconcentrations are lower (rs = -0.553). The weakcorrelation between bacteria concentrations anddissolved oxygen probably is the result of thecorrelation between water temperature anddissolved oxygen and not low dissolved oxygencausing an increase in bacteria concentration.A weak negative correlation exists betweenstreamflow and concentration of fecal coliformbacteria (rs = -0.212) and E. coli bacteria(rs = -0.231). A weak positive correlation existsbetween specific conductance and concentration offecal coliform bacteria (rs = 0.250) and E. colibacteria (rs = 0.257). As expected, a strong positivecorrelation exists between fecal coliform and E. colibacteria (rs = 0.745). When concentrations of fecalcoliform bacteria are elevated, concentrations of E.coli bacteria also are elevated.

During stormflow, a strong positive correlationexists between fecal coliform bacteria and E. colibacteria (rs = 0.612). When concentrations of fecalcoliform bacteria are elevated, concentrations ofE. coli bacteria also are elevated (table 4).

Seasonality

Seasonality in this region of temperate climateaffects bacteria concentrations in the BrandywineCreek through water temperature variations.USGS water-quality monitor stations do not collectdata between December and February. Base flowand stormflow water temperatures from 1990 to1999 at West Branch Brandywine Creek at Modena(WB9), East Branch Brandywine Creek belowDowningtown (EB10), and Brandywine Creek atChadds Ford (MS3) are grouped by month andshown in figure 7. At all three stations watertemperatures are lower during spring (March,April, and May) and fall months (September,October, and November) than during summermonths (June, July, and August).

Fecal coliform bacteria concentrations roughlyfollow the same rise and fall as water temperatures(fig. 8). The PaDEP criterion defines the swimmingseason as May 1 through September 30. Whilenone of the three stations are completely below thePaDEP criterion during the swimming season,bacteria concentrations are lowest at MS3.The 10-year median concentration of bacteria atWB9 always exceeds the PaDEP criterion of200 col/100 mL during the swimming season andcommonly exceeds the higher PaDEP criterion of2,000 col/100 mL, the criterion that pertains to theremainder of the year. However, during March,April, October, and November, some individualbacteria samples do exceed the PaDEP criterion.The 10-year median concentration of bacteria atEB10 exceeds the PaDEP swimming seasoncriterion. The remainder of the year at EB10, the10-year median concentration of bacteria does notexceed the PaDEP criterion. The 10-year medianconcentration of bacteria at MS3 exceeds thePaDEP swimming season criterion only in June.

Effect of Reser voir s

Three reservoirs are located in the BrandywineCreek Basin: Chambers Lake Reservoir (alsoknown as Birch Run Reservoir), Rock RunReservoir (also known as Coatesville Reservoir),and Marsh Creek Reservoir. Samples werecollected above and below each reservoir.A comparison of the bacteria concentrations atsites above and below each reservoir during baseflow and stormflow is shown in figure 9. Bacteriaconcentrations in streams that flow out of thereservoirs are much lower than the bacteriaconcentrations in the streams that flow into the

Table 4. Spearman rank correlations significant at the95-percent confidence interval for base-flow andstormflow samples

[n, number; rs, Spearman Rho coefficient; p-value,significance value]

Correlation n rs p-value

Base flow

Temperature - dissolved oxygen 209 -0.553 0.0001Fecal coliform - dissolved oxygen 208 -.309 .0001E. coli - dissolved oxygen 69 -.267 .0263Fecal coliform - water temperature 251 .346 .0001E. coli - water temperature 76 .351 .0018Fecal coliform - streamflow 219 -.212 .0016E. coli - streamflow 72 -.231 .0505Fecal coliform - specific conductance 243 .250 .0001E. coli - specific conductance 76 .257 .0251Fecal coliform - E. coli 76 .745 .0001

Stormflow

Fecal coliform -E. coli 32 .612 .0002

14

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EXPLANATION

25TH PERCENTILEMEDIAN75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILEDATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

RANGE OUTSIDE THE QUARTILEAND MORE THAN 1.5 TIMES THE INTERQUARTILE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILEOUTLIER DATA VALUE MORE THAN 3 TIMES THE

0

30

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Figure 7. Distribution of monthly water temperatures during base flow and stormflow at West BranchBrandywine Creek at Modena, East Branch Brandywine Creek below Downingtown and BrandywineCreek at Chadds Ford, Pennsylvania, 1990-99.

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Figure 8. Distribution of monthly fecal coliform bacteria concentrations for base flow and stormflow,West Branch Brandywine Creek at Modena, East Branch Brandywine Creek below Downingtown, andBrandywine Creek at Chadds Ford, Pennsylvania, 1990-99.

MONTH

EXPLANATION

25th PERCENTILEMEDIAN75th PERCENTILE


RANGE OUTSIDE THE QUARTILEAND MORE THAN 1.5 TIMES THE INTERQUARTILE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3


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PaDEP criterion

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WB9

EB10

MS3

16

Figure 9. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow atsampling sites above and below Chambers Lake Reservoir, Rock Run Reservoir, and Marsh CreekReservoir, Chester County, Pennsylvania, 1998-99.

25TH PERCENTILE

MEDIAN

75TH PERCENTILEINDICATES SINGLE SAMPLE

WB4 WB5 WB6 WB7 EB4 EB51

10,000

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1,000

2,000

5,000

CHAMBERS LAKE ROCK RUN MARSH CREEK

above below above below belowabove

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PaDEP criterion

RESERVOIR

RESERVOIR RESERVOIR

BASE FLOW

WB4 WB5 EB4 EB510

1,000,000

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1,000

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5,000

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EXPLANATION

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CHAMBERS LAKE MARSH CREEKRESERVOIR

STORMFLOW

RESERVOIR

PaDEP criterion

17

reservoirs. Because the volume of water flowinginto the reservoir is very small compared to thevolume of water already residing in the reservoir,the bacteria concentrations in the streams belowthe reservoirs reflect bacteria concentrations in thereservoirs, and not the bacteria concentrations inthe streams that flow into the reservoirs.

On the West Branch, Chambers Lake Reservoirand Rock Run Reservoir typically release waterfrom the bottom. The chemistry of the waterreleased from the bottom of a reservoir is differentthan the water entering from a source above thereservoir. The water at the bottom of a reservoir isusually colder (between 1 to 5°C), anoxic, and mayhave become stratified. In addition, the residencetime of the water in a reservoir is long and allowsfor natural die-off of bacteria. On the East Branch,Marsh Creek Reservoir releases water on a multi-level basis. Typically, Marsh Creek Reservoirreleases water from the middle of the reservoir.

In most cases, during storms at all threereservoirs, water flows over the top of thereservoir, reducing residence time. During largestorms, such as Hurricane Floyd on September 16,1999, water also is released from the bottom.A sample collected on July 20, 1999, during a stormat EB5 (below Marsh Creek Reservoir) had aconcentration of fecal coliform bacteria of40 col/100 mL. No sample was collected from thesite above the reservoir. On September 16, 1999,a sample collected during Hurricane Floydfrom EB4 (above Marsh Creek Reservoir)had a fecal coliform bacteria concentration of66,000 col/100 mL. The sample collected at EB5(below the reservoir) had a fecal coliform bacteria

concentration of 2,200 col/100 mL. The bacteriaconcentration below the reservoir reflects amixture of the older-residence time water beingreleased from the bottom and the younger-residence time water, which was the result of thehurricane.

COMPARISON OF BACTERIACONCENTRATIONS DURING BASE FLOW

AND STORMFLOW

Comparisons were made between bacteriaconcentrations observed during base flow andstormflow. Bacteria concentrations at five siteswhere at least four samples at each site werecollected during both base flow and stormflow arelisted in table 5. A comparison of bacteriaconcentrations during base flow and stormflow isshown in figure 10. For all five sites, bacteriaconcentrations were higher during stormflow thanduring base flow.

Storm runoff contains elevated concentrationsof bacteria. Rainfall flushes the land surface andcauses bacteria to be transported into BrandywineCreek, thereby increasing the bacteria concen-tration. Consequently, storms accelerate the influxof bacteria from any given source through land-surface runoff. In all analyses, Brandywine Creektributaries have higher bacteria concentrationsduring stormflow than during base flow. Duringstormflow, median concentrations of fecal coliformbacteria at sites on 14 of 15 tributaries (93 percent)to Brandywine Creek were greater than200 col/100 mL.

Table 5. Range and median concentrations of fecal coliform bacteria concentrations during base flow andstormflow for five sites in the Brandywine Creek Basin, Chester County, Pennsylvania, 1998-99

[FC, fecal coliform; col/100 mL, colonies per 100 milliliters; ID, identification number]

LocalID

U.S.Geological

Surveysite ID

Site name

Base flowrange of FC

concentration(col/100 mL)

Base flowFC median


Stormflowrange of FC


StormflowFC median


WB2 01480300 West Branch Brandywine Creek nearHoney Brook

63.- 10,000 4,500 1,100. - 610,000 12,000

WB8 01480500 West Branch Brandywine Creek atCoatesville Reservoir

2.- 1,800 410 3,700. - 16,000 7,200

WB9 01480617 West Branch Brandywine Creek atModena

6.- 4,400 940 2,700. - 15,000 6,000

EB10 01480870 East Branch Brandywine Creek belowDowningtown

80. - 8,000 590 1,400. - 12,000 4,500

MS3 01481000 Brandywine Creek at Chadds Ford 2. - 2,200 110 160. - 6,700 2,200

18

Figure 10. Distribution of fecal coliform bacteria concentrations during base flow and stormflow at selectedsampling sites in the Brandywine Creek Basin, Chester County, Pennsylvania, 1998-99.

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EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE


INTERQUARTILE RANGE OUTSIDE THE QUARTILEAND MORE THAN 1.5 TIMES THEOUTLIER DATA VALUE LESS THAN OR EQUAL TO 3


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WB2 WB2 WB8 WB8 WB9 WB9 EB10 EB10 MS3 MS3

LOCAL SITE NUMBER

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HATCHES DESIGNATE STORMFLOW

PaDEP criterion

19

EXTENT AND POTENTIAL SOURCES OFFECAL AND ESCHERICHIA COLI

BACTERIA

Bacteria sources were identified by examiningbacterial counts in downstream sequence. Anincrease in bacteria concentration at a samplingsite compared to the concentration at the closestupstream sampling site indicates a bacteria sourcebetween the two sites. Data on concentrations ofE. coli bacteria are noted in this section; however,the fecal coliform bacteria data provided a morecomprehensive picture of the extent and potentialsource of bacteria and were used for primaryanalysis. During base flow, 91 percent of the24 non-estimated water samples contained E. coli/fecal coliform bacteria ratios greater than 1:2.During storms, 37 percent of the eight non-estimated water samples contained E. coli/fecalcoliform bacteria ratios greater than 1:2. The datagiven in tables 6 to 11 at the back of the report arefield chemistry measurements and bacteriaconcentrations during base flow and stormflowconditions.

Bacteria concentration and land use werecompared at each of the 40 sites on the BrandywineCreek. Data for the branches and the main stemwere examined individually. Medianconcentrations of fecal coliform bacteria were usedfor a comparison between the branches and mainstem during base flow and stormflow and areshown in figures 11 and 12, respectively. Typically,elevated bacteria concentrations during base flowand stormflow indicate pollution from point andnonpoint sources. During base flow, elevatedbacteria concentrations in the Brandywine Creekappear to come from nonpoint sources such ascontaminated ground water, or from farm animalsand wildlife entering and leaving waste in thestream. During stormflow, land-surface runoff, anonpoint source, is the causal agent for theelevated bacteria concentrations in all of thesubbasins.

At base flow, the median concentrations offecal coliform bacteria at sites on the West Branchexceed 200 col/100 mL at 15 of the 20 sites(75 percent). The median concentrations of fecalcoliform bacteria at sites on the East Branch exceed200 col/100 mL at 10 of the 17 sites (58 percent).The median concentrations of fecal coliformbacteria at sites on the main stem exceed200 col/100 mL at one of the three sites(33 percent). During stormflow, the median

concentrations of fecal coliform bacteria at sites onthe West Branch exceed 200 col/100 mL at 12 of the13 sites (92 percent). The median concentrations offecal coliform bacteria at sites on the East Branchexceed 200 col/100 mL at 15 of the 17 sites(88 percent). The median concentrations of fecalcoliform bacteria at sites on the main stem exceed200 col/100 mL at all 3 sites.

Samples analyzed for E. coli bacteria werelimited in number at each site; therefore, medianconcentrations of E. coli bacteria were notdetermined for either base flow or stormflow.

West Branc h Brand ywine Creek

Distributions of fecal coliform bacteriaconcentrations in the West Branch BrandywineCreek during base flow and stormflow are shownin figure 13. During base flow, 75 percent of thesites had bacteria concentrations above the PaDEPcriterion of 200 col/100 mL. During storms,92 percent of the sites had bacteria concentrationsabove the PaDEP criterion. Of the 20 sites sampled,11 sites were on tributaries. During base flow, BirchRun, Rock Run, and Buck Run had medianbacteria concentrations below 200 col/100 mL.During stormflow, only Birch Run below theReservoir had a median bacteria concentration thatwas below 200 col/100 mL.

In the headwaters of the West BranchBrandywine Creek, fecal coliform concentrations atWest Branch Brandywine Creek at Rockville (WB1)at base flow ranged from 200 to 5,500 col/100 mL;the median was 4,100 col/100 mL. Three sampleswere analyzed for E. coli; the concentrations weregreater than 600, 1,000 and 5,900 col/100 mL. Nosamples were collected at WB1 during stormflow.West Branch Brandywine Creek at Rockville (WB1)and West Branch Brandywine Creek near HoneyBrook (WB2) are very close to one another andhave similar land uses; WB2 is at a USGSstreamflow-measurement station. Because base-flow samples at both sites were similar in bacteriaconcentration, stormflow sampling was done atWB2, and the sample was considered to berepresentative for both sites. WB1 is located in asubbasin that is predominantly agricultural(72 percent). Cows and horses are pastured in anarea upstream of WB1 that has an unfenced creek,causing a nonpoint source for bacteria during baseflow and stormflow. Farms that support crops andlivestock are within 0.5 mi upstream of WB1.

20

Figure 11. Median concentrations of fecal coliform bacteria during base flow, Brandywine CreekBasin, Chester County, Pennsylvania, 1998-99.

21

Figure 12. Median concentrations of fecal coliform bacteria during stormflow, BrandywineCreek Basin, Chester County, Pennsylvania, 1998-99.

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Figure 13. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow at samplingsites on West Branch Brandywine Creek, Chester County, Pennsylvania, 1998-99.

WB1 WBA WB2 WB3 WB4 WB5 WBBWB6 WBE WB7 WBD WBC WB8 WB9 WB10 WB11 WB12 WB13 WB14 WB151

100,000

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EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

DATA VALUE LESS THAN OR

INTERQUARTILE3 AND MORE THAN 1.5

OUTLIER DATA VALUE


PaDEP criterion

WB2 WB3 WB4 WB5 WB6 WB8 WB9 WB10 WB11 WB12 WB13 WB14 WB15

LOCAL SITE NUMBER

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BASE FLOW

STORMFLOW

DESIGNATES A TRIBUTARY

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

LESS THAN OR EQUAL TO

TIMES THE RANGE OUTSIDE THE QUARTILE

EQUAL TO 1.5 TIMES THE INTERQUARTILE RANGEOUTSIDE THE QUARTILE

23

Fecal coliform bacteria concentrations at TwoLog Run at Birdell (WBA) during base flow weremeasured three times. Concentrations were 540,740, and 960 col/100 mL. No stormflow or E. colibacteria samples were collected at this site. Thesubbasin is predominantly forested (54 percent).Cropland is within 0.5 mi upstream of WBA. Thissite, which is on a tributary below WB1 and aboveWB2, was added midway through the study tocollect additional data to evaluate the bacteriacontribution of this tributary to elevated bacteriaconcentrations measured at WB2. Although themedian concentration of fecal coliform bacteria atWBA is lower than at WB2, the medianconcentration of bacteria at WBA still exceeds thePaDEP criterion of 200 col/100 mL. Two Log Runcontributes elevated bacteria concentrations toWest Branch Brandywine Creek.

At West Branch Brandywine Creek near HoneyBrook (WB2), concentrations of fecal coliformbacteria at base flow ranged from 63 to10,000 col/100 mL; the median concentration was4,800 col/100 mL. Three samples were analyzedfor E. coli bacteria; concentrations were less than1,900, 6,600, and greater than 8,000 col/100 mL.During stormflow, the concentrations of fecalcoliform bacteria at WB2 ranged from 1,100 to610,000 col/100 mL; the median concentration was12,000 col/100 mL. Three samples were analyzedfor E. coli bacteria; concentrations were 8,000,16,000 and 250,000 col/100 mL. The maximumbacteria concentrations during stormflow for fecalcoliform and E. coli were measured duringHurricane Floyd and are not considered to benormal storm event bacteria concentrations. Thesubbasin is predominantly agricultural(68 percent). Within 0.5 mi upstream of WB2 iscropland, and horses are in a pasture that containsan unfenced stream.

Concentrations of fecal coliform bacteria atWest Branch Brandywine Creek at Brandamore(WB3) during base flow ranged from 200 to720 col/100 mL; the median concentration was250 col/100 mL. One sample was collected forE. coli bacteria; the concentration was470 col/100 mL. One stormflow sample wascollected and analyzed for E. coli bacteria; theconcentration was 1,000 col/100 mL. No stormflowsamples were measured for fecal coliform bacteria.The subbasin is predominantly agricultural(58 percent). The lower base-flow concentrations atWB3 may be attributable to the site’s distance fromWB2. The long reach of stream between the two

sites allows die-off of bacteria by deposition (intothe streambed), ultra-violet inactivation (sunlight),grazing (by protozoa and other microorganisms),or simply natural attenuation of the bacteriaresulting in a decrease in concentration.

Concentrations of fecal coliform bacteria atBirch Run near Martins Corner (WB4) during baseflow ranged from 33 to 1,400 col/100 mL; themedian concentration was 510 col/100 mL. Twosamples were collected for analysis of E. colibacteria; concentrations were 180 and230 col/100 mL. Two samples were collectedduring stormflow for analysis of fecal coliform andE. coli bacteria. Concentrations of fecal coliformbacteria were greater than 6,000 and greater than240,000 col/100 mL, and concentrations of E. colibacteria were greater than 8,000 and greater than320,000 col/100 mL. The maximum bacteriaconcentrations during stormflow for fecal coliformand E. coli were measured during Hurricane Floydand are not considered to be normal storm eventbacteria concentrations. The subbasin is predomi-nantly forested (54 percent), and the stream for0.5 mi above WB4 is forested. This site is above theChambers Lake Reservoir. Birch Run contributeselevated bacteria concentrations to Chambers LakeReservoir.

Concentrations of fecal coliform bacteria atBirch Run near Wagontown (WB5) during baseflow ranged from 3 to 33 col/100 mL; the medianconcentration was 7 col/100 mL. Both E. colibacteria sample concentrations were less than3 col/100 mL. One stormflow sample wascollected; the concentration of fecal coliformbacteria was 24 col/100 mL. No E. coli bacteriasample was collected at stormflow. The subbasin ispredominantly forested (53 percent). Because thissite is below the Chambers Lake Reservoir, it haslow bacteria concentrations. The outflow from thereservoir does not contribute elevated bacteriaconcentrations to the West Branch BrandywineCreek.

Concentrations of fecal coliform bacteria atRock Run near Philipsville (WB6) during base flowranged from 20 to 15,000 col/100 mL; the medianconcentration was 1,900 col/100 mL. Threesamples were analyzed for E. coli bacteria;concentrations were 1,400, 1,500, and1,600 col/100 mL. Two samples were analyzedfor fecal coliform and E. coli bacteria during storm-flow. Concentrations of fecal coliform bacteriawere 6,000 and 540,000 col/100 mL; E. coli bacteria

24

concentrations were 8,000 and 16,000 col/100 ml.The maximum bacteria concentrations duringstormflow for fecal coliform and E. coli weremeasured during Hurricane Floyd and are notconsidered to be normal storm event bacteriaconcentrations. The subbasin is predominantlyagricultural (58 percent). This site is above theRock Run Reservoir. Forest and cropland is within0.5 mi upstream of WB6. Rock Run contributeselevated bacteria concentrations to Rock RunReservoir.

Concentrations of fecal coliform bacteria atRock Run at Coatesville (Rock Run) Reservoir nearCoatesville (WBE) were measured twice duringbase flow. The bacteria concentrations were 3,300and 3,900 col/100 mL. No stormflow or E. colibacteria samples were collected. The subbasin ispredominantly agricultural (52 percent). This sitewas added midway through the study to collectadditional data between sites WB6 and WB7. Theright side of the creek is forested within 0.5 miupstream of WBE. On the left side, the creek runspast cropland, cattle pasture, and an open field.Site WBE is downstream from site WB6, andbacteria concentrations increase from site WB6 tosite WBE. Rock Run is usually about 20 ft in width.During the drought in 1999 when samples werecollected, Rock Run was only 4 to 5 ft wide.A possible cause for the increased concentration ofbacteria is the decrease in streamflow in Rock Runbecause of the drought.

Concentrations of fecal coliform bacteria atRock Run below Coatesville (Rock Run) Reservoir(WB7) during base flow ranged from 20 to580 col/100 mL; the median concentration was100 col/100 mL. Two samples were collected forE. coli bacteria; concentrations were 93 and97 col/100 mL. No stormflow samples werecollected. The land use in the subbasin is mixed—49 percent agriculture, 26 percent forested, and16 percent residential. Because this site is belowthe Rock Run Reservoir, bacteria concentrationsare lower than at sites WB6 and WBE, which areabove the reservoir.

Concentrations of fecal coliform bacteria forRock Run at Rock Run near Coatesville (WBD)were measured three times during base flow.The concentrations were 240, 453, and1,900 col/100 mL. No stormflow or E. coli bacteriasamples were collected. The land use in thesubbasin is mixed—47 percent agriculture,33 percent forested, and 15 percent residential.

This site was added midway through the study tocollect additional data between sites WB7 andWB8. Bacteria concentrations at site WBD, which isjust upstream from the confluence of Rock Runand the Brandywine Creek, are much higher thanat upstream site WB7, which is below the RockRun Reservoir. The land is forested and residentialwithin 0.5 mi upstream of WBD. Concrete banksline Rock Run at the sample site. Disposablediapers and rodents were present in Rock Run attimes when samples were collected. A nonpointsource for bacteria during base flow is thesurrounding urbanized area. Rock Run contributeselevated bacteria concentrations to the WestBranch Brandywine Creek.

Concentrations of fecal coliform bacteria atWest Branch Brandywine Creek at Rock Run(WBB) were measured three times during baseflow. Concentrations were 200, 210, and370 col/100 mL. No stormflow or E. coli bacteriasamples were collected. The land use in thesubbasin is mixed—48 percent agricultural,33 percent forested, and 14 percent residential.Residences and forest line the creek within 0.5 miupstream of WBB. This site was added midwaythrough the study to collect additional databetween WB7 and WB8. The Brandywine Creekabove WBB has a lower bacteria concentrationthan at WBC, which is below WBB, and receiveswater with elevated bacteria concentrations fromRock Run. The bacteria concentrations at WBBwere only slightly above the PaDEP criterion.

Concentrations of fecal coliform bacteria atWest Branch Brandywine Creek below Rock Run atCoatesville (WBC) during base flow weremeasured three times; concentrations were 250,320, and 600 col/100 mL. No stormflow or E. colibacteria samples were collected. The land use inthe subbasin is mixed—47 percent agricultural,33 percent forested, and 15 percent residential.This site was added mid-way through the study tocollect additional data between WB7 and WB8.Residences are on both sides of the creek within0.5 mi upstream of WBC. WBC is downstreamfrom site WBB, and bacteria concentrations arehigher at WBC than at site WBB.

Concentrations of fecal coliform bacteria atWest Branch Brandywine Creek at Coatesville(Rock Run) Reservoir (WB8) during base flowranged from 2 to 1,800 col/100 mL; the medianconcentration was 410 col/100 mL. Three sampleswere analyzed for E. coli bacteria; concentrations

25

were 100, 240 and 500 col/100 mL. Fecal coliformbacteria concentrations during stormflow rangedfrom 3,700 to 16,000 col/100 mL; the medianconcentration was 7,200 col/100 mL. Two sampleswere analyzed for E. coli bacteria duringstormflow; concentrations were 1,400 and12,000 col/100 mL. The maximum bacteriaconcentrations during stormflow for fecal coliformand E. coli were measured during Hurricane Floydand are not considered to be normal storm eventconcentrations. The land use in the subbasin ismixed—47 percent agricultural, 33 percentforested, 15 percent residential, and 2 percenturban (around the city of Coatesville). Residencesand forested areas line both sides of the creekwithin 0.5 mi upstream of WBB. Site WB8 is in anindustrial area of Coatesville. Bacteria concentra-tions increase between WBB and WB8. A nonpointsource for the elevated bacteria concentrationsduring base flow is the urbanized area betweenWBB and WB8.

Concentrations of fecal coliform bacteria atWest Branch Brandywine Creek at Modena(WB9) during base flow ranged from 6 to4,400 col/100 mL; the median concentration was940 col/100 mL. Concentrations of E. coli bacteriaranged from 100 to 800 col/100 mL. Fecal coliformbacteria concentrations during stormflow rangedfrom 4,000 to 15,000 col/100 mL; the medianconcentration was 6,000 col/100 mL. Threesamples were analyzed for E. coli bacteria;concentrations were 600, 2,900, and greater than8,000 col/100 mL. The land use in the subbasin ismixed—42 percent agricultural, 33 percentforested, 16 percent residential, and 4 percenturban. Approximately 1 mi upstream of WB9 is anindustrial plant with a wastewater treatment plantand a storm sewer outfall. Immediately upstreamof WB9 are residences and forested areas on theright side of the creek and an urban/industrialarea on the left side of the creek. Bacteriaconcentrations increase substantially between WB8and WB9. Nonpoint sources for bacteriacontamination are the urban area surrounding thecreek.

Concentrations of fecal coliform bacteria atBuck Run at Doe Run (WB10) during base flowranged from 7 to 370 col/100 mL; the medianconcentration was 180 col/100 mL. Two E. colibacteria samples were collected; concentrationswere 69 and 260 col/100 mL. One sample wascollected during stormflow; the concentrationof fecal coliform bacteria was greater than

6,000 col/100 mL, and the E. coli bacteriaconcentration was greater than 8,000 col/100 mL.The land use in the subbasin is predominantlyagricultural (58 percent); however, 28 percent ofthe subbasin is forested and 11 percent isresidential. At base flow, Buck Run does notcontribute elevated bacteria concentrations to DoeRun to which it is a tributary.

Concentrations of fecal coliform bacteriaat Doe Run above tributary at Springdell(WB11) during base flow ranged from 10 to1,100 col/100 mL; the median concentration was300 col/100 mL. Two samples were collected andtested for E. coli bacteria; concentrations were 110and 690 col/100 mL. One sample was collectedduring stormflow; the fecal coliform bacteriaconcentration was 580 col/100 mL. No E. colibacteria samples were collected during stormflow.The land use in the subbasin is predominantlyagricultural (76 percent). Within 0.5 mi upstreamof WB11 is cropland on the right side and horses ina fenced pasture on the left side of Doe Run. DoeRun contributes elevated bacteria concentrationsto the West Branch Brandywine Creek.

Concentrations of fecal coliform bacteria atWest Branch Brandywine Creek near Embreeville(WB12) during base flow ranged from 18 to500 col/100 mL; the median concentration was110 col/100 mL. Two water samples were collectedand tested for E. coli bacteria; concentrations were68 and 120 col/100 mL. One sample was collectedduring stormflow and analyzed for fecal coliformand E. coli bacteria; concentrations were 220 and190 col/100 mL, respectively. The subbasinsurrounding WB12 is predominantly agricultural(53 percent). Bacteria concentrations decreasebetween WB9 and WB12. The long reach betweenthe two sites and the consequent die-off of bacteriathrough deposition, UV inactivation, grazing, ornatural attenuation account for the decrease inbacteria concentration.

Concentrations of fecal coliform bacteria atLittle Broad Run near Marshallton (WB13) duringbase flow ranged from 15 to 2,000 col/100 mL; themedian concentration was 320 col/100 mL. Threesamples were analyzed for E. coli bacteria;concentrations were 200, 330, and 330 col/100 mL.Three samples were analyzed for fecal coliformbacteria during stormflow; concentrations were 24,720, and 22,000 col/100 mL. One E. coli bacteriasample was collected during stormflow; theconcentration was 670 col/100 mL. The land use in

26

the subbasin is mixed—38 percent residential,27 percent forested, and 26 percent agricultural.Within 0.5 mi upstream of WB13 is riparian forest75-120 ft wide; the remainder of the area isresidential. Little Broad Run contributes elevatedbacteria concentrations of bacteria to Broad Run.

Concentrations of fecal coliform bacteriaduring base flow at Broad Run at Northbrook(WB14) ranged from 100 to 840 col/100 mL; themedian concentration was 480 col/100 mL. Twowater samples were collected and tested forE. coli bacteria; concentrations were 46 and320 col/100 mL. One sample was collected duringstormflow; the fecal coliform bacteria concen-tration was 1,400 col/100 mL, and the E. colibacteria concentration was 1,300 col/100 mL. Theland use in the subbasin is mixed—37 percentagricultural, 29 percent forested, and 29 percentresidential. Dense riparian forest approximately90-120 ft wide is on both sides of Broad Run within0.5 mi upstream of WB14. Open, uncut fieldsextend out from the forest on both sides. A fewresidences are scattered on either side of the creekupstream. Broad Run contributes elevatedconcentrations of bacteria to the West BranchBrandywine Creek.

Concentrations of fecal coliform bacteria atWest Branch Brandywine Creek at Wawaset(WB15) during base flow ranged from 10 to350 col/100 mL; the median concentration was150 col/100 mL. Three samples were analyzed forE. coli bacteria; concentrations were 60, 200, and260 col/100 mL. One sample was collected duringstormflow; the fecal coliform bacteria concentra-tion was 3,600 col/100 mL, and the E. coli bacteriaconcentration was 1,300 col/100 mL. The land usein the subbasin is predominantly agricultural(52 percent). Bacteria concentrations increasebetween sites WB12 and WB15 as a result of BroadRun’s elevated bacteria concentrations. However,WB15’s median bacteria concentration is below thePaDEP criterion.

East Branc h Brand ywine Creek

Fecal coliform bacteria concentrations on EastBranch Brandywine Creek during base flow andstormflow are shown in figure 14. During baseflow, bacteria concentrations at 58 percent of thesites exceeded the PaDEP criterion of200 col/100 mL. During storms, bacteriaconcentrations at 88 percent of the sites exceededthe PaDEP criterion. Of the 17 sites on the EastBranch Brandywine Creek, 9 sites are located on

tributaries. Four tributaries, Indian Run, MarshCreek, Culbertson Run, and Valley Creek, hadmedian bacteria concentrations below200 col/100 mL during base flow. Only the medianbacteria concentrations at Indian Run remainedbelow 200 col/100 mL during stormflow.

Concentrations of fecal coliform bacteria in theheadwaters of the East Branch Brandywine Creekat East Branch Brandywine Creek near Cupola(EB1) during base flow ranged from 31 to1,200 col/100 mL; the median concentration was260 col/100 mL. Two samples were analyzed forE. coli bacteria; the concentrations were 86 and240 col/100 mL. Two stormflow samples werecollected and analyzed for fecal coliform bacteria;concentrations were 600 and greater than1,200 col/100 mL. No stormflow samples werecollected for analysis of E. coli bacteria. Land use inthe subbasin surrounding EB1 is predominantlyagricultural (60 percent). Within 0.5 mi upstream ofEB1 on one side is fenced farmland with cows andchickens. On the opposite side are residences.Cropland is further upstream.

Concentrations of fecal coliform bacteria atEast Branch Brandywine Creek at Glenmoore(EB2) during base flow ranged from 63 to330 col/100 mL; the median concentration was220 col/100 mL. Two samples were collected andanalyzed for E. coli bacteria; the concentrationswere 110 and 170 col/100 mL. Three samples wereanalyzed for fecal coliform bacteria duringstormflow; concentrations were 450, greater than1,200, and greater than 12,000 col/100 mL. Onesample was collected during stormflow andanalyzed for E. coli bacteria; the concentration wasgreater than 16,000 col/100 mL. EB2 is in apredominantly agricultural subbasin (53 percent).Cropland is on the right side and forest on the leftside of the creek within 0.5 mi upstream of EB2.Bacteria concentrations decrease between EB1 andEB2. One possible reason for the decrease is thechange in land use. Farm animals are replaced byforest at EB2. Overall the subbasin becomes lessagricultural and more forested than the subbasinabove EB1.

Concentrations of fecal coliform bacteria atIndian Run at Springton (EB3) were measuredthree times during base flow. The concentrationswere 11, 65, and 71 col/100 mL. One sample wascollected and analyzed for E. coli bacteria; theconcentration was 90 col/100 mL. One sample wascollected at stormflow; the fecal coliform bacteriaconcentration was 150 col/100 mL. No E. coli

27

EB1 EB2 EB3 EB6 EB7EB4 EB5 EB8 EB9 EBA EBC EB10EB13 EBB EB11 EB12 EB1410

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EB4 EB5

PaDEP criterion

Figure 14. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow atsampling sites on East Branch Brandywine Creek, Chester County, Pennsylvania, 1998-99.

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE



LOCAL SITE NUMBER

BASE FLOW

STORMFLOW

DESIGNATES A TRIBUTARY

28

bacteria samples were collected at stormflow. Theland use in the subbasin is mixed—46 percentforested, 37 percent agricultural, and 12 percentresidential. Forested areas become prevalent overagricultural areas between the subbasin above EB2and the subbasin above EB3. Median bacteriaconcentrations decrease between the twosubbasins. Indian Run does not contribute elevatedconcentrations of bacteria to East Branch Brandy-wine Creek.

Concentrations of fecal coliform bacteriaduring base flow at Marsh Creek near Glenmoore(EB4), which is above the Marsh Creek Reservoir,ranged from 12 to 200 col/100 mL; the medianconcentration was 78 col/100 mL. Two sampleswere collected and analyzed for E. coli bacteria; theconcentrations were 2 and 230 col/100 mL. Twosamples were collected during stormflow andanalyzed for fecal coliform bacteria; theconcentrations were 400 and 66,000 col/100 mL.One sample was collected and analyzed for E. colibacteria; the concentration was 2,500 col/100 mL.The second stormflow sample analyzed for fecalcoliform and E. coli bacteria was collected duringHurricane Floyd and is not considered to be abacteria concentration for a normal storm event.The land use in the subbasin is mixed—46 percentforested, 39 percent agricultural, and 8 percentresidential. At base flow, Marsh Creek does notcontribute elevated concentrations of bacteria tothe Marsh Creek Reservoir.

Concentrations of fecal coliform bacteria atMarsh Creek near Downingtown (EB5) duringbase flow were measured three times. Theconcentrations were 22, 67, and 81 col/100 mL.One E. coli bacteria sample was collected at baseflow; the concentration was 75 col/100 mL.Samples were collected twice during stormflowand analyzed for fecal coliform bacteria; theconcentrations were 40 and 2,200 col/100 mL.One sample was collected during stormflow andanalyzed for E. coli bacteria; the concentration was2,400 col/100 mL. The land use in the subbasin ismixed—38 percent forested, 34 percentagricultural, and 17 percent residential. This site isbelow Marsh Creek Reservoir. Bacteriaconcentrations decrease between EB4 and EB5. Thesecond stormflow sample analyzed for fecalcoliform and E. coli bacteria was collected duringHurricane Floyd and is not considered to be anormal storm event bacteria concentration. During

base flow, Marsh Creek does not contributeelevated bacteria concentrations to the East BranchBrandywine Creek.

Concentrations of fecal coliform bacteria atEast Branch Brandywine Creek at Lyndell (EB6)during base flow ranged from 9 to 970 col/100 mL;the median concentration was 290 col/100 mL.Two samples were collected at base flow andanalyzed for E. coli bacteria; concentrations were100 and 120 col/100 mL. Two samples werecollected during stormflow and analyzed for fecalcoliform bacteria; concentrations were 3,200 and9,200 col/100 mL. One sample was collectedduring stormflow and analyzed for E.coli bacteria;the concentration was 2,200 col/100 mL. The landuse in the subbasin is mixed—45 percentagriculture, 39 percent forested, and 10 percentresidential. Forested area is on the left side of thecreek within 0.5 mi of EB6. Approximately 150 ftupstream of EB6 is a campground. A pond on thecampground property supports fish and geese.Bacteria concentrations increase between EB2 andEB6. During base flow, nonpoint sources forbacteria include wildlife and possibly several smalltributaries between EB2 and EB6 that were notincluded in this study.

Concentrations of fecal coliform bacteria atCulbertson Run at Lyndell (EB7) during base flowranged from 9 to 430 col/100 mL; the medianconcentration was 180 col/100 mL. Two sampleswere collected during base flow and analyzed forE. coli bacteria; concentrations were 200 and340 col/100 mL. One sample was collected duringstormflow; the concentration of fecal coliformbacteria was 19,000 col/100 mL, and the concen-tration of E. coli bacteria was 960 col/100 mL. Theland use in the subbasin is mixed—44 percentagricultural, 33 percent residential, and 21 percentforested. Residences are on both sides ofCulbertson Run within 0.5 mi upstream of EB7.At base flow, Culbertson Run does not contributeelevated concentrations of bacteria to East BranchBrandywine Creek.

Concentrations of fecal coliform bacteria atEast Branch Brandywine Creek near Downing-town (EB8) during base flow ranged from 110to 170 col/100 mL; the median concentrationwas 160 col/100 mL. Two samples were analyzedfor E. coli bacteria; concentrations were 110 and170 col/100 mL. Two samples were collectedduring stormflow and analyzed for fecalcoliform bacteria and E. coli. Concentrations of

29

fecal coliform bacteria were 9,800 and16,000 col/100 mL, and concentrations of E. colibacteria were 4,000 and 4,400 col/100 mL. Themaximum bacteria concentrations duringstormflow for fecal coliform and E. coli weremeasured during Hurricane Floyd and are notconsidered to be normal storm event bacteriaconcentrations. The land use in the subbasin ismixed—39 percent agricultural, 37 percentforested, and 16 percent residential. Bacteriaconcentrations decrease between EB6 and EB8.

Concentrations of fecal coliform bacteria atBeaver Creek near Downingtown (EB9) duringbase flow ranged from 140 to 1,700 col/100 mL; themedian concentration was 700 col/100 mL.Two samples were collected at base flow andanalyzed for E. coli bacteria; concentrations were210 and 1,000 col/100 mL. Two samples werecollected during stormflow and analyzed for fecalcoliform bacteria; concentrations were 1,700 and6,800 col/100 mL. No sample was collected duringstormflow for analysis of E. coli bacteria. The landuse in the subbasin is mixed—33 percentagricultural, 29 percent forested, and 25 percentresidential. An open field, a park, and a pumpingstation are within 0.5 mi upstream from EB9.Beaver Creek contributes elevated bacteriaconcentrations to East Branch Brandywine Creek.

Concentrations of fecal coliform bacteria atEast Branch Brandywine Creek at Downingtown(EBA) during base flow were measure three times.The concentrations were 100, 210, and470 col/100 mL. Two samples were collected atbase flow and analyzed for E. coli bacteria;concentrations were 340 and 350 col/100 mL.One sample was collected during stormflow; theconcentration of fecal coliform bacteria was greaterthan 1,200 col/100 mL, and the concentration ofE. coli bacteria was greater than 800 col/100 mL.The land use in the subbasin is mixed—36 percentagricultural, 36 percent forested, and 19 percentresidential. A paper board company and the centerof the borough of Downingtown is within 0.5 miupstream of EBA. This site was added midwaythrough the study to collect additional databetween EB8 and EB10. Bacteria concentrationsincrease between EB8 and EBA. A tributarydraining a pond in the center of Downingtownflows into the East Branch Brandywine Creekabove EBA. Resident geese abound on this pondand may contribute to the slightly elevatedbacteria concentrations at EBA. During storms, thenonpoint source is land-surface runoff, exacerba-

ted by the urban areas of Downingtown. The paperboard company discharges into the local sewersystem and, therefore, is not considered to be apoint source for bacterial contamination.

Concentrations of fecal coliform bacteria atEast Branch Brandywine Creek at Altor (EBC)during base flow were analyzed three times. Theconcentrations were 200, 270, and 410 col/100 mL.No samples were collected for analysis of E. colibacteria during either base flow or stormflow. Onesample was collected during stormflow; theconcentration of fecal coliform bacteria was greaterthan 1,200 col/100 mL. The land use in thesubbasin is mixed—37 percent forested, 34 percentagricultural, and 20 percent residential. Forest,cropland, residences, and an unmannedwastewater treatment plant are within 0.5 miupstream of EBC. Another wastewater treatmentplant is approximately 1.4 mi upstream from EBC,and a paper plant is approximately 1.8 miupstream. This site was added midway throughthe study to collect additional data between EBAand EB10. Bacteria concentrations increasebetween EBA and EBC.

Fecal coliform bacteria concentrations atUwchlan Run at Exton (EB13) during base flowranged from 6 to 2,000 col/100 mL; the medianwas 310 col/100 mL. Two samples were analyzedfor E. coli bacteria; concentrations were 150 and220 col/100 mL. Two fecal coliform bacteriasamples were collected during stormflow;concentrations were 6,000 and 20,000 col/100 mL.No E. coli bacteria samples were collected duringstormflow. Uwchlan Run was dry during July andAugust 1999 and was not sampled. The land use inthe subbasin is predominantly residential(67 percent). A mixture of townhouses, open fields,forest, and urban area is within 0.5 mi upstream ofEB13. Uwchlan Run contributes elevatedconcentrations of bacteria to Valley Creek.

Samples were collected twice at Valley Creekat Ravine Road near Downingtown (EBB) duringbase flow for analysis of fecal coliform bacteria;concentrations were 31 and 60 col/100 mL. Nosamples were collected for analysis of E. colibacteria. One sample was collected duringstormflow; the concentration of fecal coliformbacteria was 70 col/100 mL. No sample wascollected during stormflow for analysis of E. colibacteria. The land use in the subbasin is mixed—31 percent forested, 26 percent residential, and20 percent agricultural. This site was added

30

midway through the study to collect additionaldata between EB13 and EB11. Bacteriaconcentrations were below the PaDEP criterion of200 col/100 mL. An instream discharge facility islocated between EB13 and EBB. The instreamdischarge is made by a quarry and consists ofground water pumped from the quarry. Groundwater contains little or no bacteria, and theaddition of ground water to the stream probablydilutes bacteria concentrations in Valley Creek.

Concentrations of fecal coliform bacteria atEast Branch Brandywine Creek belowDowningtown (EB10) during base flow rangedfrom 80 to 8,000 col/100 mL; the medianconcentration was 590 col/100 mL. One samplewas collected during base flow and analyzedfor E. coli bacteria; the concentration was110 col/100 mL. Concentrations of fecal coliformbacteria during stormflow ranged from 1,400 to12,000 col/100 mL; the median concentration was4,500 col/100 mL. Two samples were collectedduring stormflow and analyzed for E. colibacteria; the concentrations were 1,000 and16,000 col/100 mL. The maximum concentrationsfor both fecal coliform and E. coli bacteria weremeasured during Hurricane Floyd and are notconsidered to be normal storm event bacteriaconcentrations. The land use in the subbasin ismixed—37 percent forested, 34 percentagricultural, and 20 percent residential. Forest linesboth sides of the creek within 0.5 mi upstream ofEB10.

Concentrations of fecal coliform bacteria atValley Creek at Altor (EB11) during base flowranged from 40 to 220 col/100 mL. One samplewas collected during base flow and analyzedfor E. coli bacteria; the concentration was290 col/100 mL. Two samples were collectedduring stormflow and analyzed for fecalcoliform bacteria; concentrations were 1,200 and3,600 col/100 mL. One sample was collectedduring stormflow and analyzed for E. coli bacteria;the concentration was 1,600 col/100 mL. The landuse in the subbasin is mixed—33 percent forested,30 percent residential, and 19 percent agricultural.Bacteria concentrations slightly increased betweenEBB and EB11; however, Valley Creek does notcontribute elevated concentrations of bacteria toEast Branch Brandywine Creek.

Concentrations of fecal coliform bacteria atTaylor Run at Copesville (EB12) during base flowranged from 20 to 920 col/100 mL; the median

concentration was 390 col/100 mL. Two sampleswere collected at base flow and analyzed forE. coli bacteria; the concentrations were 130 to390 col/100 mL. One sample was collected duringstormflow and analyzed for fecal coliform bacteria;the concentration was 4,700 col/100 mL. Nosample was collected for analysis of E. coli bacteria.The land use in the subbasin is mixed—37 percentresidential, 26 percent forested, and 23 percentagricultural. The site is surrounded by hayfields.Taylor Run contributes elevated concentrations ofbacteria to East Branch Brandywine Creek.

Concentrations of fecal coliform bacteria atEast Branch Brandywine Creek at Wawaset(EB14) during base flow ranged from 120 to410 col/100 mL; the median concentration was230 col/100 mL. Three samples were analyzed forE. coli bacteria; concentrations were 81, 360, and410 col/100 mL. One sample was collected duringstormflow and analyzed for fecal coliform bacteria;the concentration was 280 col/100 mL. No samplewas collected during stormflow for analysis ofE. coli bacteria. The land use in the subbasin ismixed—35 percent forested, 31 percent agricul-tural, and 22 percent residential. An open field anda fenced pasture containing livestock is within0.5 mi upstream of EB14. Bacteria concentrationsdecrease between EB10 and EB14 because of thedistance between sites and the natural die-off ofthe bacteria during stream transport.

Main Stem Brand ywine Creek

Bacteria concentrations on the main stem ofthe Brandywine Creek during base flow andstormflow are shown in figure 15. At base flow, themedian bacteria concentration exceeded200 col/100 mL only at MS2 on Pocopson Creek,which is a tributary to the main stem. Duringstormflow, the median concentrations of fecalcoliform bacteria exceeded 200 col/100 mL at allthree sites.

Concentrations of fecal coliform bacteria atBrandywine Creek at Pocopson (MS1) during baseflow ranged from 2 to 85 col/100 mL; the medianconcentration was 50 col/100 mL. Two sampleswere analyzed for E. coli bacteria; concentrationswere 70 and 93 col/100 mL. Two samples werecollected during stormflow and analyzed for fecalcoliform bacteria; concentrations were 4,400 and5,500 col/100 mL. One sample was collectedduring stormflow for analysis of E. coli bacteria;the concentration was 180 col/100 mL. The land

31

0

1,200

100

200

300

400

500

600

700

800

900

1,000

1,100

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Figure 15. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow at samplingsites on main stem Brandywine Creek, Chester County, Pennsylvania,1998-99.

25TH PERCENTILEMEDIAN75TH PERCENTILE

MS1 MS2 MS3

LOCAL SITE NUMBER

100

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5,000

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100

MIL

LILI

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500

OUTLIER DATA VALUE MORE THAN

STORMFLOW

BASE FLOW

DESIGNATES TRIBUTARY

EXPLANATION


PaDEP criterion

PaDEP criterion

RANGE OUTSIDE THE QUARTILE 3 TIMES THE INTERQUARTILE

MS1 MS2 MS3

32

use in the subbasin is mixed—42 percentagricultural, 32 percent forested, and 17 percentresidential. Bacteria concentrations decreasebetween EB14 on the East Branch and WB15 on theWest Branch and MS1. This decrease inconcentration is due to the distance between sitesand the natural die-off of the bacteria.

Concentrations of fecal coliform bacteria forPocopson Creek at Pocopson (MS2) during baseflow ranged from 3 to 1,100 col/100 mL; themedian concentration was 430 col/100 mL. Threesamples were analyzed for E. coli bacteria;concentrations were 20, 80, and 390 col/100 mL.Two samples were collected during stormflow andanalyzed for fecal coliform bacteria; concentrationswere 15,000 and 20,000 col/100 mL. No sampleswere collected during stormflow for analysis ofE. coli. The land use in the subbasin is mixed—49 percent agricultural, 26 percent residential, and21 percent forested. A hayfield is on the upstreamright side and horses are pastured on the left side.Approximately 300 ft upstream is riparian forest90-120 ft wide on both sides of the creek. PocopsonCreek contributes elevated bacteria concentrationsto the main stem Brandywine Creek.

Concentrations of fecal coliform bacteria atBrandywine Creek at Chadds Ford (MS3) duringbase flow ranged from 2 to 2,200 col/100 mL; themedian concentration was 120 col/100 mL. Twosamples were collected at base flow and analyzedfor E. coli bacteria; concentrations were 44 and180 col/100 mL. Concentrations of fecal coliformbacteria during stormflow ranged from 160 to6,700 col/100 mL; the median concentration was2,200 col/100 mL. Two samples were collectedduring stormflow and analyzed for E. coli bacteria;concentrations were 440 and 620 col/100 mL.Bacterial concentrations increase between sitesMS1 and MS3; however, the median concentrationdoes not exceed the PaDEP criterion. A nonpointsource for the increase in bacteria concentrationduring base flow is Pocopson Creek, a tributarybetween sites MS1 and MS3 with elevated bacteriaconcentrations.

Point Disc harges

Eighteen point discharges are known in theBrandywine Creek Basin. The point discharges areidentified as wastewater treatment plants andinstream discharge facilities. Instream dischargefacilities are commercial and industrial, such aspaper mills and steel plants. The quality of the

water being discharged from the wastewatertreatment plants and the instream dischargefacilities at the time of sampling was notdetermined. Each wastewater treatment plantmust submit a Discharge Monitoring Report(DMR) to the PaDEP and resolve any exceedancein bacteria concentrations. It was beyond the scopeof this project to research and evaluate eachfacility’s record of DMR’s. While any one of thepoint discharges in the Brandywine Creek Basinoccasionally could be a point source for bacteriacontamination, they are not viewed as causalagents because of their regulation by the PaDEP.

SUMMARY AND CONCLUSIONS

Concentrations of fecal coliform bacteria atthree USGS long-term water-quality monitoringstations in the Brandywine Creek Basin show ageneral downward trend for 1973-99. Implemen-tation of regulations stemming from of the CleanWater Act of 1972 contributed to the decrease ofbacteria concentrations between 1973 and 1987.With the upgrade in wastewater treatment plants,a decrease in point-source discharges, and thegeneral decrease of agricultural land use in thebasin, bacteria concentrations decreaseddramatically and then stabilized. Concentrationsof fecal coliform bacteria were highest at WestBrandywine Creek at Modena and lowest atBrandywine Creek at Chadds Ford. Streamflowand concentrations of fecal coliform bacteria werepositively related at both sites, that is, bacteriaconcentrations increase as streamflow increases.Concentrations of fecal coliform bacteria areelevated—they exceed the regulatory criterion of200 colonies per 100 milliliters—during both baseflow and stormflow conditions at all threemonitoring stations.

The concentrations of fecal coliform and E. colibacteria in the Brandywine Creek Basin wereassessed on the basis of data collected at 40 streamsites. Thirty-two sampling sites were selected onthe basis of historical data, land use, known pointdischarges of bacteria, and areas whererecreational use was evident; nine of these siteswere at established U.S. Geological Survey (USGS)streamflow-measurement stations. Eightadditional sampling sites were added midwaythrough the study to collect additional databetween established sites with elevated bacteriaconcentrations measured during monthlysampling. Sampling was conducted at base flowapproximately monthly from March to September

33

1999. Sampling also was conducted during fivestorms where rainfall exceeded 0.5 in. Sampleswere collected at all of the USGS streamflow-measurement stations during every storm, and fiveselected sites were sampled during each storm.

During 1998-99, the median concentration offecal coliform bacteria in the water samplescollected during base flow in the BrandywineCreek Basin exceeded 200 col/100 mL at 26 sites(65 percent). The median concentration of fecalcoliform bacteria at sites sampled on the WestBranch exceeded 200 col/100 mL at 15 of the20 sites (75 percent). The median concentration offecal coliform bacteria at sites sampled on the EastBranch exceeded 200 col/100 mL at 10 of the17 sites (58 percent). The median concentration offecal coliform bacteria on the main stem exceeded200 col/100 mL at one of the three sites(33 percent). During 1998-99, the medianconcentration of fecal coliform bacteria in thewater samples collected during stormflowexceeded 200 col/100 mL at 30 of 33 sites(91 percent). The median concentration of fecalcoliform bacteria at sites on the West Branchexceeded 200 col/100 mL at 12 of 13 sites sampled(92 percent). The median concentration of fecalcoliform bacteria at sites on the East Branchexceeded 200 col/100 mL at 15 of the 17 sitessampled (88 percent). The median concentration offecal coliform bacteria on the main stem exceeded200 col/100 mL at all three sites sampled.

Every water sample analyzed contained E. colibacteria. During base flow, in 21 of 24 samples(91 percent of non-estimated measurements) theratio of E. coli to fecal coliforms was greater than1:2. During stormflow, in 2 of 8 samples (37 percentof non-estimated measurements) the ratio of E. colito fecal coliforms was greater than 1:2.

The Kruskal-Wallis test for statisticallysignificant differences in bacteria concentrations atthe 95-percent confidence level showed nosignificant differences between fecal coliformconcentrations in agricultural, forested, residentialor mixed subbasins during base flow andstormflow. However, sites in forested subbasinshad a greater range in bacteria concentrations thandid sites in agricultural, residential, or mixedsubbasins.

Factors affecting bacteria concentrations in theBrandywine Creek Basin include nonpoint sources,stormflow, reservoirs, and seasonality. Nonpointsources may include agriculture, ground-water

contamination (residential septic systems orleaking landfills), urban/residential activities,resident wildlife, and land-surface runoff.

Bacteria concentrations are higher instormflow than in base flow. Rainfall flushes theland surface, and overland runoff transportsbacteria into the stream. The bacteriaconcentrations at five sites where at least foursamples were collected during both base flow andstormflow were compared. For all five sites,bacteria concentrations were substantially higherduring storms than during base flow. Duringstormflow, sites on 14 of 15 tributaries(93 percent) to Brandywine Creek had medianconcentrations of fecal coliform bacteriagreater than 200 col/100 mL.

Sites above and below each of the threereservoirs in the Brandywine Creek Basin(Chambers Lake, Rock Run, and Marsh CreekReservoirs) were sampled. Bacteria concentrationsin the streams that flow from the reservoirs arelower than bacteria concentrations in the streamsthat flow into the reservoirs. The bacteriaconcentration in the water flowing out of thereservoir is reflective of the bacteria concentrationin the reservoir, not the stream flowing into thereservoir. The volume of water in the incomingstream is very small compared to the volume ofwater in the reservoir.

Seasonality plays a role in the concentration ofbacteria in Brandywine Creek. During March,April, May, October, and November, watertemperatures and bacteria concentrations arelower in the Brandywine Creek than during June,July, August, and September. The 10-year medianconcentrations of bacteria at West BranchBrandywine Creek at Modena and East BranchBrandywine Creek below Downingtown exceededthe criterion of 200 col/100 mL established by thePaDEP for the swimming season. The 10-yearmedian concentrations of bacteria at BrandywineCreek at Chadds Ford exceeded criterion of200 col/100 mL only during June. None of thethree stations exceeded the criterion of2,000 col/100 mL established by the PaDEP forthe remainder of the year.

Tributaries on the West Branch that contributeelevated bacteria concentrations to BrandywineCreek during base flow include Birch Run, RockRun, Doe Run, Little Broad Run, Broad Run, andTwo Log Run. During stormflow, Buck Run alsocontributes elevated bacteria concentrations.

34

Tributaries on the East Branch that contributeelevated bacteria concentrations to BrandywineCreek during base flow include Beaver Creek,Uwchlan Run, and Taylor Run. During stormflow,Marsh Creek, Culbertson Run, and Valley Creekalso contribute elevated bacteria concentrations.Pocopson Creek, the only tributary on the mainstem that was evaluated, contributes bacteriaconcentrations to the Brandywine Creek duringbase flow and stormflow.

SELECTED REFERENCES

Chester County, 1996, Landscapes-Managingchange in Chester County 1996-2000—Comprehensive Plan Policy Element:West Chester, Pa., 128 p.

Clesceri, L.S., Greenberg, A.E., and Eaton, A.D.,eds., 1998, Standard methods for theexamination of water and wastewater, 20thedition: Washington, D.C., American PublicHealth Association, American Water WorksAssociation, and Water EnvironmentFederation [variously paged].

Dufour, A.P., 1977, Escherichia—the fecal coliform,in Hoadley, A., and Dutka, B.J., eds., Bacterialindicators/health hazards associated withwater: American Society for Testing andMaterials, STP 635, p. 48-58.

Francy, D.S., Myers, D.M., and Metzker, K.D., 1993,Escherichia coli and fecal coliform bacteria asindicators of recreational water quality:U.S. Geological Survey Water-ResourcesInvestigations Report 93-4083, 34 p.

Grieg, D., Bowers, J., and Kauffman, G., 1998,Christina River Basin Water QualityManagement Strategy, Phase I & II: WaterResources Agency for New Castle County,

Chester County Conservation District, andChester County Water Resources Authority,Chester County, Pa. [variously paginated]

Myers, D.N., and Wilde, F.D., eds., 1997, Biologicalindicators: U.S. Geological SurveyTechniques of Water-Resources Investigations,book 9, chap. A7, 38 p.

Pennsylvania Department of EnvironmentalProtection, 1999, Pennsylvania Code, Title 25,Chapter 93, Water Quality Standards:Commonwealth of Pennsylvania, 212 p.

U.S. Environmental Protection Agency, 1986,Quality criteria for water 1986: Office ofWater, EPA 440/5-86-001 [variously paged].

_____1998, Bacterial water quality standards forrecreational waters: Office of Water, EPA 823-R-98-003, [variously paged]

Wilde, F.D., Radtke, D.B., Givs, J., and Iwatsubo,R.T., 1998, National field manual for thecollection of water-quality data: U.S.Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A4[variously paginated].

Wilhelm, L.J., and Maluk, T.L., 1998, Fecal-indicator bacteria in surface waters of theSantee River Basin and coastal drainages,North and South Carolina, 1995-98:U.S. Geological Survey Fact Sheet 085-98,6 p.

Wood, C.R., 1998, The U.S. Geological Surveycooperative water-resources program inChester County, Pennsylvania: U.S.Geological Survey Fact Sheet 067-98, 4 p.

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Table 6. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during base flow, West Branch Brandywine Creek Basin, Chester County,Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; µS/cm, microsiemens per centimeter at 25°C;mg/L, milligrams per liter; E, estimated; >, greater than; <, less than; —, no data; mL, milliliter]

DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)

Specificconductance

(µS/cm)

Tempera-ture(°C)

Fecalcoliform(colonies

per100 mL)

E. coli(colonies

per100 mL)

WB1 West Branch Brandywine Creek at Rockville (01480269)

08-04-98 — — — 291 20.5 5,500 —04-09-99 — 12.4 7.3 274 11.5 200 —05-05-99 3.5 10.9 7.0 271 13.5 1,900 E —06-04-99 3.1 8.2 7.0 279 20.0 5,000 —07-19-99 .60 7.1 7.4 293 24.5 3,100 >60008-16-99 .72 6.5 7.1 286 23.5 5,100 5,90009-13-99 .93 7.5 7.0 302 17.0 4,100 1,000

WBA Two Log Run at Birdell (01480295)

07-19-99 1.1 8.5 7.8 276 20.0 540 —08-16-99 — 9.6 7.3 278 17.5 960 —09-13-99 — 9.2 7.4 294 16.5 740 —

WB2 West Branch Brandywine Creek near Honey Brook (01480300)

07-29-98 3.3 — — 280 23.0 6,600 E —08-04-98 2.7 — — 308 21.0 4,100 —04-09-99 5.9 9.8 7.0 288 12.0 63 —05-05-99 5.3 10.3 7.3 — 14.5 2,300 E —06-04-99 2.0 7.2 7.1 327 19.0 4,800 —07-19-99 .70 — 7.7 405 25.0 >6,000 >8,00008-16-99 .70 6.5 7.6 382 23.0 >6,000 6,60009-13-99 .87 7.8 7.4 372 19.0 10,000 1,900 E

WB3 West Branch Brandywine Creek at Brandamore (01480349)

07-29-98 9.9 — — 246 23.0 270 —09-24-98 — — — 254 14.0 230 —05-04-99 17 10.8 7.6 237 15.0 200 —06-02-99 11 8.1 7.1 210 20.5 200 —07-19-99 — 8.5 7.8 255 24.0 720 47008-16-99 3.0 7.0 7.1 272 21.5 590 —

WB4 Birch Run near Martins Corner (01480390)

07-29-98 .81 8.7 7.6 118 19.0 1,400 —04-08-99 2.0 9.1 8.2 104 17.0 33 —05-04-99 1.8 10.9 7.5 100 14.5 300 E —06-02-99 .86 9.1 6.8 89 17.5 130 18007-19-99 — 8.3 7.1 98 22.0 650 —08-16-99 .19 8.4 6.8 128 19.5 510 —09-13-99 .23 8.8 6.8 151 16.0 820 230 E

WB5 Birch Run near Wagontown (01480400)

07-29-98 2.0 6.8 7.3 135 18.0 28 E —04-08-99 4.0 9.9 6.9 123 12.5 3 E —05-05-99 3.4 10.0 7.2 127 14.0 3 E 3 E

06-03-99 1.7 8.4 7.0 135 13.0 7 E 1 E

09-13-99 1.7 7.8 6.9 150 20.0 33 —

36

WB6 Rock Run near Philipsville (01480458)

07-29-98 1.2 — — 180 20.5 2,400 —04-08-99 1.8 9.5 8.9 165 18.5 20 E —05-04-99 1.6 10.8 8.1 164 15.5 1,600 E —06-02-99 .98 8.5 7.0 181 20.5 15,000 E >1,60007-19-99 — 8.0 7.6 191 22.5 870 E 1,40008-16-99 .39 8.0 7.2 214 21.0 2,100 1,500 E

WBE Rock Run at Reservoir near Coatesville (01480463)

08-04-99 — — — — 19.5 3,900 —08-16-99 — — — 232 20.0 3,300 —

WB7 Rock Run below Coatesville Reservoir (01480466)

07-29-98 1.2 — — 202 19.5 33 E —09-24-98 — — — 300 12.5 580 —05-05-99 1.4 11.4 8.6 192 16.5 20 E —05-18-99 .93 8.6 6.8 193 12.0 100 9309-13-99 1.1 6.8 6.7 215 21.0 120 97

WBD Rock Run at Rock Run near Coatesville (01480470)

07-19-99 — — — — 21.5 1,900 E —08-17-99 — — — — 19.5 453 —09-13-99 — — — 276 16.0 240 —

WBB West Branch Brandywine Creek at Rock Run (01480434)

07-19-99 — — — — 22.5 370 —08-17-99 — — — — 23.0 210 —09-13-99 — — — 283 16.0 200 —

WBC West Branch Brandywine Creek below Rock Run at Coatesville (01480480)

07-19-99 — — — — 23.0 600 —08-17-99 — — — — 22.5 320 —

09-13-99 — — — 270 16.5 250 —

WB8 West Branch Brandywine Creek at Coatesville Reservoir (01480500)

07-27-98 20 — — 233 21.5 1,800 E —08-04-98 20 — — 236 19.5 280 100 E

09-24-98 12 — — 251 13.0 410 —04-07-99 36 12.1 8.3 213 15.5 2 E —05-05-99 32 9.6 7.3 228 13.5 130 —05-18-99 25 9.8 7.4 221 14.0 410 24006-01-99 3.7 9.2 7.6 232 22.0 >600 —07-19-99 8.1 8.3 7.3 236 25.0 420 —08-16-99 9.8 10.0 7.7 254 23.5 330 —09-13-99 8.4 9.3 7.2 254 17.5 450 500

Table 6. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during base flow, West Branch Brandywine Creek Basin, Chester County,Pennsylvania, July 1998 to September 1999—Continued


DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)

Specificconductance

(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

37

WB9 West Branch Brandywine Creek at Modena (01480617)

07-07-98 38 10.0 7.7 316 21.5 500 —07-13-98 30 10.2 7.8 313 21.5 820 —07-27-98 27 9.6 8.3 330 22.5 940 —08-04-98 26 — — 337 20.5 1,800 100 E

08-24-98 26 11.8 8.2 338 24.0 1,500 E —09-09-98 6.5 10.5 7.6 314 18.0 3,000 —09-22-98 23 8.5 7.7 359 22.0 2,100 —03-11-99 46 12.9 8.2 285 4.0 150 —04-08-99 43 12.0 9.2 301 17.5 6 E —04-16-99 59 10.4 7.6 265 11.5 390 —04-29-99 42 8.3 7.6 283 12.0 240 —05-03-99 38 8.3 7.8 296 13.5 280 —05-18-99 33 9.7 7.8 307 16.0 1,400 E 80005-25-99 43 10.2 7.8 276 17.5 2,800 —06-02-99 28 10.3 7.8 298 22.5 480 —06-23-99 23 10.8 8.2 335 22.5 2,000 E —06-28-99 19 7.3 7.5 356 23.0 2,100 —07-15-99 15 11.3 8.2 368 21.0 2,200 E —07-19-99 13 8.4 7.8 409 24.5 2,300 —07-26-99 14 10.2 8.4 395 25.5 750 —08-03-99 13 9.5 8.0 402 24.5 1,300 —08-16-99 16 9.1 8.2 380 25.5 860 66009-08-99 30 7.8 7.6 333 22.5 4,400 —09-13-99 16 8.1 7.9 433 16.0 610 310

WB10 Buck Run at Doe Run (01480629)

07-28-98 13 — — 223 22.0 190 —04-07-99 23 11.9 7.8 215 12.0 7 E —05-04-99 21 11.2 7.5 214 14.0 18 E —06-02-99 16 9.1 7.3 217 23.5 170 —08-16-99 7.1 9.5 7.7 236 23.5 310 26009-13-99 8.6 9.1 7.1 246 17.0 370 69 E

WB11 Doe Run above Tributary at Springdell (014806318)

07-29-98 — — — 152 19.5 200 —04-07-99 12 11.6 7.6 153 12.5 10 E —05-04-99 11 11.9 7.1 155 13.0 82 —06-03-99 6.9 8.8 7.0 155 18.5 1,100 69007-19-99 4.2 8.7 7.3 152 23.0 620 —08-16-99 2.1 8.9 7.1 148 22.5 360 —09-13-99 3.8 10.0 7.0 155 16.5 300 110 E



DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)

Specificconductance

(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

38

WB12 West Branch Brandywine Creek near Embreeville (01480634)

07-28-98 66 — — 266 22.0 260 —04-08-99 123 11.3 8.0 240 12.0 18 E —05-03-99 112 11.3 8.1 236 13.0 93 —06-01-99 84 9.4 7.6 262 22.0 500 E —07-19-99 38 9.4 7.5 291 24.5 130 12008-16-99 39 8.2 7.4 297 23.0 85 E 68 E

WB13 Little Broad Run near Marshallton (01480637)

07-29-98 .37 — — 251 19.0 450 —08-04-98 .37 — — 254 17.0 260 20004-08-99 .73 11.6 8.0 235 14.0 15 E —05-03-99 .63 10.4 6.9 249 12.5 27 E —06-01-99 .42 8.5 7.1 250 19.5 140 —07-19-99 .21 8.8 7.0 254 21.0 2,000 E —08-16-99 .35 9.0 7.1 249 20.5 530 330 09-13-99 .09 9.8 7.2 243 15.5 380 330

WB14 Broad Run at Northbrook (01480638)

07-28-98 4.2 8.7 7.7 195 19.0 480 —05-18-99 5.4 9.5 7.3 190 15.0 100 46 E

07-19-99 1.2 9.3 7.1 194 20.5 840 —08-16-99 .80 8.4 7.0 208 20.5 720 —09-13-99 1.7 9.7 7.2 203 15.0 470 320

WB15 West Branch Brandywine Creek at Wawaset (01480640)

07-28-98 70 8.9 7.9 254 22.5 350 —04-08-99 134 10.5 8.7 231 14.5 10 E —05-03-99 101 8.9 7.0 226 13.0 120 —06-01-99 77 9.9 7.1 238 22.5 150 —07-21-99 40 8.4 7.7 284 23.5 220 20008-18-99 28 7.2 7.3 288 24.0 200 E 26009-14-99 36 8.9 7.6 294 19.0 100 60 E



DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)

Specificconductance

(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

39

Table 7. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during base flow, East Branch Brandywine Creek Basin, Chester County,Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; µS/cm, microsiemens per centimeter at 25°C;mg/L, milligrams per liter; E, estimated; —, no data; mL, milliliter]

DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)

Specificconduc-

tance(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

EB1 East Branch Brandywine Creek near Cupola (01480648)

03-31-99 4.4 10.6 8.3 203 13.5 31 E —05-04-99 3.7 13.3 8.5 220 15.5 140 —06-02-99 2.2 8.2 6.5 217 18.5 1,200 —08-03-99 .44 8.6 7.3 219 19.0 260 E 24008-17-99 .57 7.6 7.3 228 20.0 260 86 E

EB2 East Branch Brandywine Creek at Glenmoore (01480653)

03-31-99 14 12.2 7.6 191 8.0 63 E —05-04-99 14 11.5 7.4 201 12.5 200 —06-02-99 8.0 8.9 6.7 200 21.5 160 17008-03-99 — 6.9 7.0 200 20.0 330 —08-17-99 2.6 7.7 7.2 209 21.0 270 —09-15-99 1.7 7.9 7.0 228 18.0 220 E 110 E

EB3 Indian Run at Springton (01480658)

03-31-99 5.8 12.3 8.5 158 12.5 11 E —05-04-99 4.2 11.0 8.5 177 14.5 65 —06-02-99 3.2 8.9 6.8 183 18.5 71 E 90

EB4 Marsh Creek near Glenmoore (01480675)

07-29-98 2.7 8.3 7.6 201 21.0 78 —03-31-99 8.2 11.4 7.2 182 9.0 14 E —05-04-99 6.9 10.4 6.9 191 12.5 12 E 2 E

06-02-99 3.0 8.3 6.7 183 20.5 100 —08-17-99 .76 7.9 7.1 241 21.5 200 230

EB5 Marsh Creek near Downingtown (01480685)

7-29-98 9.0 7.2 8.0 169 26.5 22 E —05-04-99 5.2 10.2 7.2 197 13.5 67 7508-03-99 8.7 7.6 6.4 203 10.0 81 E —

EB6 East Branch Brandywine Creek at Lyndell (01480660)

07-27-98 14 — — 197 20.0 430 —03-31-99 29 12.2 8.5 187 13.5 9 E —05-05-99 23 11.2 7.6 223 17.5 67 —06-02-99 12 8.6 6.6 197 23.0 970 E 12008-03-99 3.6 9.4 7.4 201 20.5 440 —09-14-99 5.7 9.4 7.2 217 17.0 140 E 100 E

EB7 Culbertson Run at Lyndell (01480662)

07-27-98 3.5 — — 237 20.0 180 —03-31-99 5.0 11.9 8.1 228 12.5 9 E —05-05-99 4.9 10.7 7.3 254 13.5 120 —08-17-99 .34 8.1 7.2 237 21.5 300 34009-14-99 .72 8.8 7.2 257 17.0 430 200

40

EB8 East Branch Brandywine Creek near Downingtown (01480700)

07-27-98 41 — — 200 23.0 160 —08-04-98 38 — — 203 20.0 170 —03-31-99 66 12.3 6.6 212 6.5 110 —05-04-99 39 11.1 7.5 218 13.0 160 17006-02-99 39 9.0 7.8 206 22.0 110 110

EB9 Beaver Creek near Downingtown (01480775)

07-28-98 7.7 8.2 — 350 19.0 490 —03-31-99 18 12.5 7.2 315 8.0 140 —05-03-99 15 10.2 7.9 312 12.5 740 —06-02-99 9.0 8.8 7.6 324 21.0 1,700 E 1,00008-03-99 2.2 9.2 7.7 405 20.5 1,200 E —08-17-99 2.3 8.3 7.6 403 20.5 700 —09-14-99 4.0 9.0 7.6 383 17.5 140 E 210

EBA East Branch Brandywine Creek at Downingtown (01480800)

08-03-99 17 11.4 8.3 282 23.5 100 35008-17-99 — — 8.4 267 23.0 470 34009-14-99 — 12.5 8.3 285 19.5 210 —

EBC East Branch Brandywine Creek at Altor (01480840)

08-03-99 19 7.3 7.4 354 21.5 410 —08-17-99 — — 7.4 363 23.5 200 —09-14-99 — — 7.5 402 20.0 270 —

EB13 Uwchlan Run at Exton (01480878)

07-29-98 1.5 — — 401 21.0 480 —08-04-98 .30 — — 412 19.0 230 22003-31-99 1.2 13.5 8.6 415 10.0 6 E —05-04-99 .65 11.8 7.8 407 13.5 200 15006-04-99 .30 8.2 7.2 406 18.5 2000 —09-14-99 .04 8.1 7.8 417 18.0 390 220

EBB Valley Creek at Ravine Road near Downingtown (01480887)

08-03-99 1.6 8.5 7.6 584 22.0 60 E —08-17-99 — — — 575 24.0 31 E —

EB10 East Branch Brandywine Creek below Downingtown (01480870)

07-07-98 76 9.0 7.8 286 21.1 480 —07-13-98 101 9.4 7.4 261 21.5 590 —07-27-98 65 10.9 8.3 307 23.0 340 —08-04-98 61 — — 309 20.5 880 —08-10-98 59 8.7 7.7 308 24.0 300 —08-18-98 112 8.4 7.4 220 22.0 > 600 —08-24-98 68 9.8 7.9 304 24.0 520 —09-09-98 55 9.3 7.7 304 18.5 640 —09-22-98 65 8.0 7.4 329 21.0 >8,000 —

Table 7. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during base flow, East Branch Brandywine Creek Basin, Chester County,Pennsylvania, July 1998 to September 1999—Continued


DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)

Specificconduc-

tance(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

41

03-31-99 114 13.8 7.7 265 8.5 80 E —04-29-99 84 10.4 7.5 286 12.5 190 —05-03-99 80 11.3 7.7 295 14.0 660 —05-18-99 69 9.9 7.8 285 16.0 150 11006-02-99 71 6.7 7.7 303 22.0 530 —06-23-99 58 9.6 7.9 334 23.5 1,600 E —06-28-99 52 6.2 7.5 342 24.0 390 —07-15-99 43 8.5 7.7 386 20.5 390 E —07-19-99 38 6.4 7.4 405 24.0 470 —07-26-99 42 8.0 7.7 360 24.5 920 —08-03-99 35 6.8 7.4 390 24.0 680 —08-16-99 42 6.8 7.6 349 24.5 550 —09-08-99 48 6.6 7.3 330 23.0 4,000 —09-14-99 49 6.8 7.5 379 20.0 410 —

EB11 Valley Creek at Altor (01480905)

07-27-98 9.0 11.8 8.4 400 21.0 83 E —03-31-99 24 10.6 7.5 398 6.5 40 E —05-03-99 18 11.2 8.0 375 12.0 77 —06-04-99 11 11.0 8.0 334 22.0 220 29008-03-99 2.5 8.0 7.5 332 21.0 88 E —08-17-99 4.7 9.1 7.6 444 22.0 200 —

EB12 Taylor Run at Copesville (01480930)

07-28-98 4.7 12.3 8.6 518 25.0 580 —03-31-99 7.0 13.0 7.7 500 14.5 20 E —05-03-99 6.8 10.9 7.4 426 12.5 200 —06-02-99 4.9 — 7.8 489 22.0 390 —08-03-99 2.1 7.4 7.1 706 20.5 920 —08-17-99 2.3 7.3 7.0 591 22.5 800 39009-14-99 3.0 10.7 7.7 530 19.0 250 130 E

EB14 East Branch Brandywine Creek at Wawaset (01480950)

07-28-98 56 7.3 7.6 346 22.0 410 —05-03-99 — 10.8 7.2 330 13.0 120 —06-02-99 59 — 7.4 335 22.0 220 —07-21-99 31 7.6 7.2 392 23.0 230 36008-18-99 24 6.9 7.4 408 24.0 330 41009-14-99 28 9.0 7.4 415 21.5 130 E 81 E

Table 7. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during base flow, East Branch Brandywine Creek Basin, Chester County,Pennsylvania, July 1998 to September 1999—Continued


DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)

Specificconduc-

tance(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

42

Table 8. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during base flow, main stem Brandywine Creek Basin, Chester County,Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; µS/cm, microsiemens per centimeterat 25°C; mg/L, milligrams per liter; E, estimated; >, greater than; —, no data; mL, milliliter]

DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)

Specificconduc-tance

(µS/cm)

Tempera-ture(oC)

Fecal coliform(colonies

per100 mL)

E. coli(colonies

per100 mL)

MS1 Brandywine Creek at Pocopson (01480970)

07-28-98 139 — — 293 23.0 15 E —09-24-98 — 8.3 7.8 305 16.0 28 E —04-08-99 — 13.0 7.6 265 15.0 2 E —06-01-99 146 9.2 6.8 283 22.5 63 E —08-18-99 53 8.0 7.4 319 26.0 83 9309-15-99 43 7.3 7.2 347 20.5 85 E 70

MS2 Pocopson Creek at Pocopson (01480975)

07-28-98 3.3 — — 232 21.0 430 —09-24-98 — 12.1 8.1 222 13.0 620 —04-08-99 — 11.5 8.0 215 15.0 3 E —05-03-99 7.9 10.6 6.9 220 11.0 1,100 —06-01-99 4.6 9.1 6.8 — 19.5 1,100 —07-21-99 2.1 8.8 7.5 234 22.0 420 39008-18-99 .39 8.1 7.3 244 22.5 130 E 80 E

09-15-99 1.7 8.5 7.1 248 19.0 240 20 E

MS3 Brandywine Creek at Chadds Ford (01481000)

07-07-98 195 8.3 7.5 300 22.0 180 —07-13-98 222 7.5 7.7 283 21.5 60 E —07-27-98 162 8.0 7.5 313 23.0 120 —08-10-98 122 7.5 7.4 330 25.0 580 —08-18-98 382 — 7.2 190 23.0 > 600 —08-24-98 131 7.5 7.2 316 24.0 120 —09-09-98 131 8.0 7.5 260 19.0 88 —09-22-98 116 6.6 7.4 341 22.0 210 —09-24-98 106 5.2 7.6 365 17.0 60 E —03-11-99 265 10.0 6.3 267 4.0 27 —04-07-99 294 12.3 7.9 265 13.5 2 E —04-16-99 348 10.0 7.5 229 11.5 52 —04-29-99 241 9.7 7.4 258 13.5 98 —05-03-99 219 9.3 7.4 262 14.5 78 —05-18-99 195 10.1 7.7 275 18.0 94 E 44 E

06-02-99 173 8.2 7.6 277 23.0 110 —06-23-99 163 10.0 7.4 293 22.0 150 E —06-28-99 135 6.5 7.0 303 25.0 100 —07-15-99 104 8.4 7.5 321 22.0 2,200 E —07-19-99 85 6.5 7.4 341 26.5 180 —07-21-99 104 7.4 7.4 293 25.0 110 —07-26-99 80 7.1 7.5 338 26.5 120 —08-03-99 63 6.0 7.4 372 26.0 180 —08-16-99 92.3 7.8 7.5 316 25.5 105 —09-08-99 181 7.6 7.4 271 24.5 210 —09-15-99 99.7 7.8 7.7 335 21.5 140 180

43

Table 9. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during storms, West Branch Brandywine Creek Basin, Chester County,Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; µS/cm, microsiemens per centimeter at 25°C;mg/L, milligrams per liter; E, estimated; >, greater than; —, no data; mL, milliliter]

DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)


(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

WB2 West Branch Brandywine Creek near Honey Brook (01480300)

10-08-98 20 — — 265 16.0 150,000 E —03-22-99 92 10.9 7.2 203 6.5 1,100 —08-14-99 10 — — 294 23.0 >6,000 >8,00008-26-99 4 — — 219 19.01 >12,000 >16,00009-16-99 202 — — 116 17.5 610,000 E 250,000

WB3 West Branch Brandywine Creek at Brandamore (01480349)

08-26-99 — — — 238 20.0 — 1,000WB4 Birch Run near Martins Corner (01480390)

08-14-99 — — — 145 22.0 >6,000 >8,00009-16-99 — — — 119 17.5 >240,000 >320,000

WB5 Birch Run near Wagontown (01480400)

03-22-99 40 12.9 7.1 123 6.0 24 E —WB6 Rock Run near Philipsville (01480458)

08-14-99 — — — 218 23.0 > 6,000 > 8,00009-16-99 — — — 118 18.0 540,000 E 16,000 E

WB8 West Branch Brandywine Creek at Coatesville Reservoir (01480500)

10-08-98 40 — — 209 15.5 3,700 —03-22-99 734 12.7 7.71 139 5.0 5,100 —08-26-99 25 — — 172 20.0 9,200 1,400 E

09-16-99 410 — — — 18.0 16,000 12,000WB9 West Branch Brandywine Creek at Modena (01480617)

10-08-98 51 — — 243 17.5 15,000 —03-22-99 817 12.7 7.8 146 5.0 5,000 —08-14-99 21 5.7 7.7 328 26.0 > 6,000 > 8,00008-26-99 38 6.1 7.7 252 20.5 11,000 E 600 E

09-16-99 596 3.1 7.5 410 19.0 4,000 2,90009-27-99 30 9.0 8.0 377 17.5 2,700 E —

WB10 Buck Run at Doe Run (01480629)

08-14-99 — — — 220 27.0 > 6,000 > 8,000WB11 Doe Run above Tributary at Springdell (014806318)

10-08-98 12 11.6 7.6 153 15.5 580 —WB12 West Branch Brandywine Creek near Embreeville (01480634)

08-14-99 — — — 210 26.5 220 190

WB13 Little Broad Run near Marshallton (01480637)

10-08-98 2.1 — — 165 16.5 22,000 —03-22-99 2.0 11.1 7.7 209 9.0 24 E —08-14-99 — — — 249 24.0 720 670

WB14 Broad Run at Northbrook (01480638)

08-14-99 — — — 197 23.5 1,400 E 1,300WB15 West Branch Brandywine Creek at Wawaset (01480640)

08-26-99 — — — 263 21.0 3,600 E 1,300

44

Table 10. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during storms, East Branch Brandywine Creek Basin, Chester County, Pennsylvania,July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; µS/cm, microsiemens per centimeterat 25 °C; mg/L, milligrams per liter; E, estimated; >, greater than; —, no data; mL, milliliter]

DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)


(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

EB1 East Branch Brandywine Creek near Cupola (01480648)

07-30-98 2.4 — — 224 21.0 600 —07-20-99 .67 7.6 7.5 227 21.5 > 1,200 —

EB2 East Branch Brandywine Creek at Glenmoore (01480653)

07-30-98 8.5 — — 211 21.5 450 —07-20-99 5.4 6.8 7.1 204 22.0 >1,200 —08-26-99 — — — 173 19.5 >12,000 >16,000

EB3 Indian Run at Springton (01480658)

07-30-98 2.5 — — 191 20.0 150 —EB4 Marsh Creek near Glenmoore (01480675)

03-22-99 100 12.2 6.7 146 5.5 400 E —09-16-99 320 — — 188 18.0 66,000 2,500

EB5 Marsh Creek near Downingtown (01480685)

07-20-99 8.5 7.5 7.0 200 9.5 40 E —09-16-99 10 — — 281 12.0 2,200 2,400

EB6 East Branch Brandywine Creek at Lyndell (01480660)

07-20-99 10 7.6 7.7 185 22.5 3,200 —08-26-99 — — — 158 19.0 9,200 2,200

EB7 Culbertson Run at Lyndell (01480662)

08-26-99 — — — 240 19.5 19,000 E 960 E

EB8 East Branch Brandywine Creek near Downingtown (01480700)

08-26-99 94 — — 181 18.0 9,800 >4,00009-16-99 588 — — — 18.0 16,000 4,400

EB9 Beaver Creek near Downingtown (01480775)

07-20-99 4.0 8.8 7.2 356 21.5 6,800 —08-26-99 — — — 248 19.5 1,700 E —

EBA East Branch Brandywine Creek at Downingtown (01480800)

07-20-99 — 9.7 8.4 262 22.0 > 1,200 > 800EBC East Branch Brandywine Creek at Altor (01480840)

07/20/99 39 9.4 7.1 388 23.5 >1,200 —EB13 Uwchlan Run at Exton (01480878)

10-08-98 6.2 — — 106 18.0 20,000 E —07-20-99 .34 8.9 7.3 285 23.5 > 6,000 —

EBB Valley Creek at Ravine Road near Downingtown (01480887)

07-20-99 — 6.0 7.4 299 23.0 70 E —EB10 East Branch Brandywine Creek below Downingtown (01480870)

03-22-99 973 11.4 7.4 152 6.5 2,100 —05-25-99 132 9.4 7.7 244 18.0 4,500 —07-20-99 59 5.5 7.2 342 24.5 6,500 E —08-26-99 142 3.9 7.0 220 20.5 5,000 1,00009-16-99 1,210 4.2 7.4 166 19.5 12,000 16,00009-27-99 398 7.0 7.2 232 16.0 1,400 E —

45

EB11 Valley Creek at Altor (01480905)

07-20-99 8.1 9.5 7.0 240 23.5 > 1,200 —08-26-99 — — — 148 21.0 3,600 E 1,600

EB12 Taylor Run at Copesville (01480930)

07-20-99 3.3 8.2 7.1 516 23.5 4,700 —EB14 East Branch Brandywine Creek at Wawaset (01480950)

08-26-99 — — — 167 21.0 280 E —

Table 10. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteriaconcentrations during storms, East Branch Brandywine Creek Basin, Chester County, Pennsylvania,July 1998 to September 1999—Continued

[°C, degrees Celsius; ft3/s, cubic feet per second; µS/cm, microsiemens per centimeterat 25 °C; mg/L, milligrams per liter; E, estimated; >, greater than; —, no data; mL, milliliter]

DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)


(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

46

Table 11. Streamflow, physical and chemical properties, and fecal coliform and E. colibacteria concentrations during storms, Main Stem Brandywine Creek Basin, Chester County,Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; µS/cm, microsiemens per centimeterat 25°C; mg/L, milligrams per liter; E, estimated; —, no data; mL, milliliter]

DateDischarge

(ft3/s)

Oxygen,dissolved

(mg/L)

pH(standard

units)


(µS/cm)

Tempera-ture(°C)


per100 mL)

E. coli(colonies

per100 mL)

MS1 Brandywine Creek at Pocopson (01480970)

10-09-98 — — — 200 16.5 4,40009-16-99 — — — 347 20.5 5,500 180 E

MS2 Pocopson Creek at Pocopson (01480975)

10-09-98 — — — 186 16.0 15,000 —09-16-99 — — — 108 20.0 20,000 E —

MS3 Brandywine Creek at Chadds Ford (01481000)

03-22-99 3,620 11.4 7.4 150 6.5 2,200 —05-25-99 409 8.3 7.4 210 16.0 6,700 —08-26-99 747 7.3 7.4 300 22.0 2,600 62009-16-99 8,290 7.4 7.1 125 17.0 960 E 440 E

09-27-99 395 8.8 7.6 257 16.5 160 —

historical trends and concentrations of fecal coliform bacteria in the

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